LIVE - Updated at 13:20
Man arrested after people killed in city centre; counter-terrorism police understood to be assisting investigation.
A witness, Lynn Haggitt, has said she saw a van hitting two people in Nottingham. She told Channel 4 News:
At half past five, I saw a van pull up at the side of me. It was white, all white. There was a police car behind it coming up slowly, no flashing lights. The man in the driver's seat looked in his mirror and saw the police car behind him.
She said the white van then drove up to "the corner of the street and went into two people".
The lady ended up on the kerb, and then he backed up the white van and he went, speeded up Parliament Street with the police cars following him.
Asked if the people hit were hurt badly, she said a man appeared to have a head injury. "They did get him to his feet," she added, and said of the woman who was hit: "She was sitting up on the kerb, to me she looked OK".
Another witness in Nottingham has described the moment she saw a man and a woman hit by a van, with her account tallying largely with that given in respect of the same incident by Lynn Haggitt (see 11.09am).
Frances, who did not publicly give her surname, told Sky News she was on her way to work and was near Theatre Royal in the city centre when she saw the van hit the two people.
There was a male and a female. The female, she could speak. She was in pain from the impact of hitting the ground. She had hit her head but was still able to speak. Then the gentleman as well took the full brunt of the van and he had head injuries but was still awake. He didn't lose consciousness, he was still awake at that stage.
There was a male and a female. The female, she could speak. She was in pain from the impact of hitting the ground. She had hit her head but was still able to speak.
Then the gentleman as well took the full brunt of the van and he had head injuries but was still awake. He didn't lose consciousness, he was still awake at that stage.
Speaking to the same broadcaster, she has added:
I just got off the bus with around 40 other people and we were walking along Market Square to catch our next bus, crossed over the road at Theatre Royal and got around 10ft down the road when all of a sudden we heard a bang which sounded like a vehicle hitting a bollard. I turned around and then saw the two people on the floor, on the road. Someone was screaming. I think a gentleman ran over to help as well. The police were there straight away, then the ambulance arrived and they got the two people in the ambulance and got them sent off to whichever hospital.
I just got off the bus with around 40 other people and we were walking along Market Square to catch our next bus, crossed over the road at Theatre Royal and got around 10ft down the road when all of a sudden we heard a bang which sounded like a vehicle hitting a bollard.
I turned around and then saw the two people on the floor, on the road. Someone was screaming. I think a gentleman ran over to help as well.
The police were there straight away, then the ambulance arrived and they got the two people in the ambulance and got them sent off to whichever hospital.
Armed police officers, some wearing balaclavas, have been seen on Ilkeston Road, a few hundred yards above the main cordon, the PA news agency reports.
Police appeared to enter a commercial property on the street, with two young women eventually put in the back of a marked car. Several unmarked police vehicles carrying armed officers then left, after the section of the road was cordoned off.
Here's a map showing where the incidents we know of so far happened:
We reported earlier that a van was being guarded by police on a street to the north-west of Nottingham city centre (see 11.46am). A little more detail from the PA news agency, which says that - viewed from the other side of the cordon - the van has clear damage to its bonnet and windscreen.
There are two dents on the bonnet, just above the radiator grille, and two sets of corresponding cracks radiating out from two points on the windscreen, the agency reports.
Residents gathered at the cordon said they were disturbed by shouting just before 5.30am, but that this was not unusual because the street is home to several drug rehabilitation establishments.
A witness has told the BBC he saw a young man and young woman being stabbed on Ilkeston Road, close to the junction with Bright Street in Nottingham, at about 4am.
The man, who did not give his name, told the broadcaster he heard "awful, bloodcurdling screams" and looked out his window to see a "black guy dressed all in black with a hood and rucksack grappling with some people".
She was screaming 'Help!' I just wish I'd shouted something out of the window to unnerve the assailant. I saw him stab the lad first and then the woman. The lad collapsed in the middle of the road. The girl stumbled towards a house and didn't move. The next minute she had disappeared down the side of a house, and that's where they found her. I'd say it all happened within five or six minutes.
She was screaming 'Help!' I just wish I'd shouted something out of the window to unnerve the assailant. I saw him stab the lad first and then the woman. The lad collapsed in the middle of the road.
The girl stumbled towards a house and didn't move. The next minute she had disappeared down the side of a house, and that's where they found her. I'd say it all happened within five or six minutes.
The man said he called the police, who arrived within five minutes, before paramedics tried to revive the pair for 40 minutes.
Two police patrol cars were parked inside a cordon near the TK Maxx store on Milton Street, with armed police present, the PA news agency reports.
An adjacent cordon stretching several hundred metres along Mansfield Road was also in place, in the direction of the fatality in Magdala Road. A person who entered the Milton Street cordon shorty before 11.30am was taken to the ground by police officers near a McDonald's restaurant, before being carried to a police van and driven away.
The area around a white Vauxhall Vivaro van left on a street to the north-west of Nottingham city centre has been cordoned off, the PA news agency reports.
The van had been left a short distance from the pavement, with its passenger door open, and what looked like a black bag on the road near the door. Police were guarding the cordon by a convenience store. However, they were staying clear of the vehicle, with no forensic activity evidently under way.
Kane Brady, a student at the University of Nottingham, told GB News he saw a knife being taken from a white van after a man was arrested outside his house on the street.
We woke up to shouts of 'armed police' and what . sounded like some very loud noises, what sounded like gunshots - it was that loud. I looked out the bedroom window and saw Tasers. I saw a man being dragged out [of the van] and pinned to the floor. I saw him getting arrested, him trying to resist. I then later saw when they opened the van, I saw a large knife being pulled out and then straight away that's when police closed off both roads, both Maples Street and Bentinck Road.
We woke up to shouts of 'armed police' and what . sounded like some very loud noises, what sounded like gunshots - it was that loud.
I looked out the bedroom window and saw Tasers. I saw a man being dragged out [of the van] and pinned to the floor. I saw him getting arrested, him trying to resist.
I then later saw when they opened the van, I saw a large knife being pulled out and then straight away that's when police closed off both roads, both Maples Street and Bentinck Road.
Police cordoned off around 400 yards of the scene at Ilkeston Road with tape, and what appeared to be medical kit was scattered across the road.
The PA news agency reports that two forensic officers arrived and appeared to spend the majority of their time at a bathroom and plumbing business called Willbond. The forensic officers eventually left the scene on foot with a black crate and large plastic bag.
The home secretary, Suella Braverman, has said she is saddened at the deaths in Nottingham, and has spoken with the chief constable of Nottinghamshire police. She tweeted:
I am shocked and saddened that three people have lost their lives today in Nottingham. My thoughts are with those affected by this incident ... I am thankful to the emergency services for their response.
The prime minister, Rishi Sunak, has said his thoughts are with those who have lost loved ones. He tweeted:
I want to thank the police and emergency services for their ongoing response to the shocking incident in Nottingham this morning. I am being kept updated on developments. The police must be given the time to undertake their work. My thoughts are with those injured, and the family and loved ones of those who have lost their lives.
The MP for Nottingham North, Alex Norris, has said the community sends its thoughts and prayers after the incident. He tweeted:
Awful news for our city to wake up to today. Our community's thoughts and prayers are with all those affected. Our gratitude is with our blue light responders for their work today also.
The city's two professional football clubs, Nottingham Forest and Notts County, have reacted to the incident. The former has tweeted:
We are devastated to learn the news of the horrific events that took place in Nottingham this morning. The thoughts of everyone at #NFFC are with the friends and families of those who have tragically lost their lives and to everyone affected by this incident.
The latter said the news was "devastating".
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Related: Tell us: have you been affected by the situation in Nottingham?
Here's a quick roundup of the substantial updates we've had:
Three people have been found dead in Nottingham, in what police described as a "horrific and tragic incident"
A 31-year-old man was arrested on suspicion of murder after two people were found dead in the street in Ilkeston Road just after 4am on Tuesday. A third man was found dead in Magdala Road, Nottinghamshire police said
Another three people are in hospital after someone tried to run them over in a van in Milton Street, in what police believe was a connected incident
Counter-terror police are helping with the investigation, though this does not necessarily mean the incident is believed to be an act of terrorism
Nottingham's three members of parliament - Nadia Whittome, Alex Norris and Lilian Greenwood - have released a joint statement on this morning's incident:
Our city has been devastated by the deaths of three people this morning. Our thoughts and prayers are with the families and loved ones of those who have died and those injured. We are grateful for the efforts of the city's emergency responders in tackling these incidents. They must be allowed to do their jobs in investigating them. Nottingham is a beautiful city, home to brilliant people from all backgrounds. We are shaken by today's events but will meet them collectively as a community and heal together.
Our city has been devastated by the deaths of three people this morning. Our thoughts and prayers are with the families and loved ones of those who have died and those injured.
We are grateful for the efforts of the city's emergency responders in tackling these incidents. They must be allowed to do their jobs in investigating them.
Nottingham is a beautiful city, home to brilliant people from all backgrounds. We are shaken by today's events but will meet them collectively as a community and heal together.
Keir Starmer, the Labour leader, addressed the incident during a talk at London Tech Week this morning.
There has been a serious incident in Nottingham this morning . Three people have lost their lives, so I'm sure I speak for everybody in this room when I say we'd like to just send our thoughts to all those affected and the emergency services who are responding to this as we speak.
Counter-terrorism police are understood to be assisting the investigation as detectives try to understand what triggered the incidents. Regular police remain in the lead, several hours after the first attack, which was just after 4am.
The three attacks have not been declared a terrorist incident, with police urgently investigating the background of the man they have in custody as they try to determine a motive.
To understand what happened, police will try to find and examine any phones or computers the suspect used.
Road closures in place include Ilkeston Road, Milton Street, Maples Street and Woodborough Road, from the junction with Magdala Road into the city.
The tram network is also disrupted, with all services suspended on the Nottingham Express Transit (NET) as the police investigation continued.
Glen Gretton, a local resident, said he was woken up at around 5am on Tuesday morning by the sounds of a series of police cars passing his home. The 46-year-old delivery driver, who lives in a flat in Mansfield Road in Sherwood, told the PA news agency:
I heard a police car go past. It was driving extremely quickly, followed by another one, another one. They just kept coming so I knew something quite major ... was happening somewhere around the city centre.
We've got a bit more detail from Nottinghamshire police.
Chief constable Kate Meynell said:
This is an horrific and tragic incident which has claimed the lives of three people. We believe these three incidents are all linked and we have a man in custody. This investigation is at its early stages and a team of detectives is working to establish exactly what has happened. We ask the public to be patient while inquiries continue. At this time, a number of roads in the city will remain closed as this investigation progresses.
This is an horrific and tragic incident which has claimed the lives of three people.
We believe these three incidents are all linked and we have a man in custody.
This investigation is at its early stages and a team of detectives is working to establish exactly what has happened.
We ask the public to be patient while inquiries continue. At this time, a number of roads in the city will remain closed as this investigation progresses.
A 31-year-old man has been arrested on suspicion of murder after three people were killed in Nottingham city centre early this morning.
A Nottinghamshire police statement read:
A man has been arrested on suspicion of murder after three people were killed in the city. Police were called to Ilkeston Road just after 4am where two people were found dead in the street. Officers were then called to another incident in Milton Street where a van had attempted to run over three people. They are currently being treated in hospital. A man has also been found dead in Magdala Road. Police have arrested a 31-year-old man on suspicion of murder and he remains in police custody.
A man has been arrested on suspicion of murder after three people were killed in the city.
Police were called to Ilkeston Road just after 4am where two people were found dead in the street.
Officers were then called to another incident in Milton Street where a van had attempted to run over three people. They are currently being treated in hospital.
A man has also been found dead in Magdala Road.
Police have arrested a 31-year-old man on suspicion of murder and he remains in police custody.
This is a developing situation and we will bring you the latest updates as we get them.
Police have said two people were found dead in the street in Ilkeston Road just after 4am this morning.
A third man was found dead in Magdala Road.
Another three people are in hospital after someone tried to run them over in a van in Milton Street, in what police believe is a connected incident.
A 31-year-old man has since been arrested.
Police have said they are still "working to establish exactly what has happened".