Violence broke out at about 12:30 am (2330 GMT Saturday) in and around the Arcadian Centre, a popular venue filled with restaurants, nightclubs and bars.
West Midlands Police confirmed “a number” of stabbings but said it had no information on reports that shots had been fired. No further details on casualties were immediately available.
The incident comes after several previous mass casualty stabbings, including one in the Scottish city of Glasgow on June 26, in which six people were injured, including a police officer.
A man was charged with murder after three people were killed in a park in Reading, west of London, the previous week in an attack investigated by counter-terrorism police.
Police guard a cordon on Livery Street following a major stabbing incident in the centre of Birmingham (AFP photo)
Britain has been on high alert after two mass stabbings in London in the last year, which saw both perpetrators — convicted extremists released early from prison — shot dead by armed officers.
Knife crime in England and Wales increased six percent in the year to the end of March, according to the Office for National Statistics.
Birmingham, one of Britain’s most ethnically diverse cities with a population of more than one million, has had an explosive recent history of gang violence.
In January 2003, one gang opened fire with an illegal semi-automatic sub-machine gun at a rival group. Two teenage girls who were bystanders were killed in the hail of bullets.
Cara Curran, a nightclub promoter, was working at the Arcadian Centre on Saturday night.
She told AFP she saw “groups upon groups” of people fighting in and around the venue and heard the use of “racial slurs”.
“I had seen a lot of tensions building through the night, which wasn’t quite like what I’ve seen before,” she said.
“I had left with my boyfriend. I heard a commotion and saw multiple police coming towards our direction. I headed towards where I saw them coming and it all just unfurled in front of me.”
“It was quite a street fight. It didn’t really look like fighting. It was just multiple people on top of each other, not one on one.”
Curran said the violence caused people in the area to flee the scene.
Police and other emergency services arrived quickly and cordoned off the area.
The elected mayor of the West Midlands Andy Street said there had been a “series of incidents” in the Hurst Street area, which is in the heart of the city’s Gay Village district.
“They look to be related but the motivation for them is not yet understood. The area is calm and the advice to the public is to go about their business as normal,” he told BBC television
Television footage showed forensic specialists in protective clothing poring over the scene, which was taped off and guarded by officers.
“Work is still going on to establish what has happened, and could take some time before we are in a position to confirm anything,” West Midlands Police said.
“At this early stage it would not be appropriate to speculate on the causes of the incident.”
Watch Several stabbed in ‘major incident’ at Birmingham: British police