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Police have launched a murder investigation after being called to reports of stabbings in Birmingham city centre in the early hours of Sunday.
One man died, another man and a woman suffered serious injuries, while five others received injuries which were not thought to be life-threatening.
Chief Superintendent Steve Graham said there was "absolutely no suggestion" the attacks were terror related.
West Midlands Police are hunting for one suspect in relation to the attacks.
The force released a statement, saying: "Detectives are following a number of lines of enquiry and we've increased our uniformed and armed response in the city.
"We continue to hold a number of scenes across the city, including Livery Street, Irving Street and Hurst Street.
"We're urging anyone who witnessed anything or anyone who has any CCTV or mobile phone footage to get in contact as soon as possible, as the information you have may be crucial to our investigation."
Chief Superintendent Steve Graham, responsible for policing in Birmingham, said: "The events during the early hours of this morning are tragic, shocking and understandably frightening.
"Please be assured that we are doing absolutely everything we can to find whoever was responsible and try to understand what exactly happened."
Anyone with information is asked to contact us via Live Chat on our website or call 101.
The BBC's Nick Clitheroe, at the scene, said it had unfolded in a part of Birmingham where the area known as the Gay Village meets the Chinese Quarter, which is typically busy at night with clubs and bars.
He added: "This appears to have started out as a major fight between large groups of people but obviously at some point knives have been pulled and stabbings have taken place."
"This will be very worrying for all the people living around here."
Our correspondent added that there had also been activity on Irving Street, less than half a mile away from the original epicentre of the incident.
"There is a blue tent covering something, the collision investigations unit is here too... The police have got an awful lot on their hands."
A "major incident" describes any situation involving serious harm or a security risk to the public.
It also means special arrangements are in place for all of the emergency services to work together.
'Shell-shocked'
Witness Cara Curran, a club promoter working in the Arcadian Centre, said it had been busier during the evening than it had been at any time since the start of lockdown.
She said she had finished her shift at about 00:30 BST and was drinking with colleagues when she heard a "loud bang and quite a lot of commotion".
Image caption Cara Curran was finishing work when witnessing what appeared to be a mass brawlShe added: "I found multiple people having fist fights... people from inside pubs and clubs came out and started to see what was going on.
"There were females, males, old people, young people, such a mix of people, it didn't seem real at the time.
"Working on the club scene for over two years, I've always seen quite a lot of fights but it was nothing like tonight. The body language and demeanour was quite different.
"The amount of things that I've heard have happened tonight in the space of three hours, with the stabbings that have happened, the car crashes and multiple other things, it's such a huge shock to me.
"For me to be an eyewitness to something that has happened, it's been quite an emotional night to the point where I'm actually still a bit shell-shocked."
The streets in the area have already been closed to traffic due to coronavirus restrictions.
Image copyright Reuters Image caption Police say it is "not appropriate" to speculate on the motivation Image copyright PA Media Image caption Police have cordoned off much of Hurst StreetSpeaking on BBC1's Andrew Marr Show, Foreign Secretary Dominic Raab said: "We know it's a very serious incident and our thoughts and prayers are with the victims and their families.
"We don't know too much more than that but we advise people to stay very vigilant."
Asked if it might be terror-related, he said: "I haven't got any information to that extent."
Image copyright @ShauninBrum Image caption Police set up a cordon at the junction of Hurst Street and Bromsgrove StreetEarlier the force said there had not been any reports of gunshots, adding: "We're aware of some comments that gunshots were fired, this has not been reported to us at this stage."
Outside the cordoned-off area, much of the city centre, such as Birmingham's Bullring shopping centre and the Sealife Centre in Brindleyplace, is open as usual.
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