Media playback is unsupported on your device
A man who killed one man and wounded seven others during a two-hour stabbing rampage across Birmingham city centre remains at large, police said.
The first stabbing was in Constitution Hill at 00:30 BST and the killer moved south, apparently attacking at random, officers said.
The stabbings do not appear terrorism-related, gang-related or connected to disorder, West Midlands Police said.
The force urged anyone with CCTV or mobile footage to contact them.
Police said they were hunting a single suspect.
One man died, another man and a woman suffered serious injuries, while five others received injuries which were not thought to be life-threatening.
Ch Supt Steve Graham said the attacker went on to stab people in Livery Street, Irving Street and finally in Hurst Street at about 02:20 BST.
He said officers - some armed - remained across the city centre to reassure people.
Mr Graham said: "The events during the early hours of this morning are tragic, shocking and understandably frightening.
"It does appear to be a random attack because we haven't found any links between the victims, either in their nature or in where they were socialising.
"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 the incidents 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."
'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.
"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."
Image copyright @ShauninBrum Image caption Police set up a cordon at the junction of Hurst Street and Bromsgrove StreetA statement released by West Midlands Police said: "Detectives are following a number of lines of inquiry and we've increased our uniformed and armed response in the city.
"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."
The force, which earlier launched a major incident, 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."
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.
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.
Were you in the area? Did you witness what happened? Share your experiences by emailing haveyoursay@bbc.co.uk.
Please include a contact number if you are willing to speak to a BBC journalist. You can also get in touch in the following ways:
WhatsApp: +44 7756 165803 Tweet: @BBC_HaveYourSay Please read our terms & conditions and privacy policy