Multiple people have been injured and a major incident declared after a series of stabbings in Birmingham.
Police and paramedics were called to reports of a knife attack in the early hours of Sunday, with further stabbings then being reported.
One witness told BBC Radio 5 Live that the attack seemed like "one group of boys against another group of boys".
West Midlands Police said there were "a number" of victims, but the severity of their injuries was not immediately known.
The force denied reports of gunshots being fired, and added "it would not be appropriate to speculate on the causes of the incident".
A witness, Cara, told 5 Live she had heard racial slurs during the incident, adding that it was a "multicultural night" in the clubs near the Arcadian Centre.
Pictures of the Week: August 30 - September 5
Pictures of the Week: August 30 - September 5
Sixth form pupils socialize at the King Edward VI High School for Girls in Birmingham, England, Thursday, Sept. 3, 2020, as schools across England reopen to students following the coronavirus lockdown. Millions of children are returning to school across Europe and beyond in a mass experiment aimed at bridging inequalities and resuscitating economies despite the persistent pandemic. Governments are trying to show that life goes on despite a virus that has infected at least 25 million people worldwide and killed more than 850,000. (Jacob King/PA via AP)
A woman dressed as Mr Punch during the demonstration.
Outside the HM Treasury buildings Protesters at the Extinction Rebellion Carnival of Corruption marched towards Buckingham Palace but were blocked by police at The Mall. Activists demand for those in power to take action on climate and environment issues. (Photo by Dave Rushen / SOPA Images/Sipa USA)
PLYMOUTH, ENGLAND - SEPTEMBER 03: The large scale artwork ‘Speedwell’, named after the Mayflower's sister ship, lights up the harbour as part of the commemorations of the 400th Anniversary of the sailing of the Mayflower on September 03, 2020 in Plymouth, United Kingdom. Speedwell uses illuminated signage to ask complex questions about our world, this damaged planet, and how we arrived at this pivotal moment in history. It offers multiple readings; constantly shifting between words that are lit up, questioning the historic conceit that there ever was a ‘New World’; and asking us to imagine new worlds of living, caring and dying well together. Speedwell was created by Still/Moving, an artist collective of Laura Hopes, Martin Hampton and Léonie Hampton who developed the concept with guidance from representatives of the indigenous peoples of North America. (Photo by Finnbarr Webster/Getty Images)
A protester dressed as a clown during the demonstration.
Extinction Rebellion Carnival of Corruption protesters march from Parliament Square to Trafalgar Square where they held a sit down protest, Police moved in and made arrests. Activists demand for those in power to take action on climate and environment issues. (Photo by Dave Rushen / SOPA Images/Sipa USA)
LONDON, ENGLAND - SEPTEMBER 03: Steven Finn , Max Holden , Dan Lincoln and Luke Hollman of Middlesex celebrate after the dismissal of Ryan ten Doeschate of Essex during the Vitality Blast T20 match between Middlesex and Essex Eagles at Lord's Cricket Ground on September 03, 2020 in London, England. (Photo by Alex Davidson/Getty Images)
A passenger ferry heads down the River Mersey as a fisherman works on the beach at Crosby, England, Thursday Sept. 3, 2020. (Peter Byrne/PA via AP)
A demonstrator is guarded by a police officer during an Extinction Rebellion climate change protest at Parliament Square in London, Wednesday, Sept. 2, 2020. Hundreds of protesters gathered near Parliament to urge returning lawmakers to support a climate emergency bill and to prepare for a climate crisis. (AP Photo/Kirsty Wigglesworth)
Human rights lawyer Geoffrey Nice sits at his desk at his home in Adisham, England, Wednesday, Sept. 2, 2020. The prominent British human rights lawyer is convening an independent tribunal in London with public hearings next year, to look into the Chinese government's alleged rights abuses against the Uighur Muslim minority in the far western province of Xinjiang. (AP Photo/Frank Augstein)
A platform at Canary Wharf Underground station in London. Workers are being encouraged to return to their offices, with a Government PR blitz commencing this week reminding people about the efforts taken to make workplaces "Covid-secure". (Photo by Victoria Jones/PA Images via Getty Images)
MALTON, ENGLAND - SEPTEMBER 02: A family attend a screening of The Greatest Showman during the Luna Cinema movie experience at Castle Howard on September 02, 2020 near Malton, England. The Luna Cinema will be showing movies at Castle Howard over several evenings allowing visitors to view from specially arranged socially distanced pitches on the lawn within the grounds of the North Yorkshire stately home. (Photo by Ian Forsyth/Getty Images)
BRADFORD, ENGLAND - SEPTEMBER 02: An Albion Sports player celebrates following the FA Cup Extra Preliminary Round between Campion and Albion Sports on September 02, 2020 in Bradford, England. (Photo by George Wood/Getty Images)
Protesters marching with placards, flags and banners during the demonstration.
The Northern Rebellion, which is part of the Extinction Rebellion movement, take to the Streets for two weeks of action under the slogan of �We Want To Live�. (Photo by Andy Barton / SOPA Images/Sipa USA)
Photocall for Atelier Picasso. The exhibition will reimagine Picasso�s Cannes Studio as an immersive experience within the gallery, using a treasure trove of objects including furniture, sculptures, ceramics, drawings and prints, held at Bastian gallery in Central London, UK on September 1, 2020. (Photo by Claire Doherty/Sipa USA)
Groundsmen work around the pitch area after Pakistan innings during the third Twenty20 cricket match between England and Pakistan, at Old Trafford in Manchester, England, Tuesday, Sept. 1, 2020. (AP Photo/Jon Super, Pool)
Passengers ride in an Underground train during the rush hour in London. The Prime Minister said people were returning in "huge numbers to the office" but Downing Street said it could not yet provide information to back up the claim. (Photo by Victoria Jones/PA Images via Getty Images)
A woman without a face mask enters an underground station during coronavirus pandemic.
It is mandatory to wear face masks while travelling. (Photo by Dinendra Haria / SOPA Images/Sipa USA)
SALTBURN BY THE SEA, ENGLAND - SEPTEMBER 01: A cat sits on the beach at sunrise on September 01, 2020 in Saltburn By The Sea, England. Today will be largely fine and dry for most today with sunny spells and gentle winds. (Photo by Ian Forsyth/Getty Images)
Kathryn Bryce of Lightning during the Rachel Heyhoe Flint Trophy match between Northern Diamonds and Loughborough Lightning at Emirates Riverside, Chester le Street, England, on August 31, 2020. (Photo by Mark Fletcher/MI News/NurPhoto via Getty Images)
People enjoy the Bank Holiday weather on the eastern strip of the beach at Bournemouth. PA Photo. Picture date: Monday August 31, 2020. Forecasters predicted this Bank Holiday Monday could be the coldest on record for some parts of the UK as temperatures are expected to be well below average for the time of year. See PA story WEATHER BankHoliday. Photo credit should read: Jonathan Brady/PA Wire
A man fishing in the early morning light as the sun rises over Blyth pier in Northumberland on the first day of Meteorological autumn. (Photo by Owen Humphreys/PA Images via Getty Images)
Pilates instructor Juliana Campos poses in her carnival costume in Notting Hill, London, on what would have been the weekend of the Notting Hill Carnival, after the 2020 carnival was cancelled due to the coronavirus pandemic, Sunday, Aug. 30, 2020. (Yui Mok/PA via AP)
Sasha Johnson Co-organiser of the Million People March and Black Lives Matter activist takes part during the demonstration.
Organisers say the Million People march is intended to revive the original spirit of the carnival, which began as an attempt to resolve racial tensions in the capital. (Photo by Thabo Jaiyesimi / SOPA Images/Sipa USA)
Denmark's Rasmus Hojgaard poses with the trophy after winning the ISPS HANDA UK Championship at The Belfry, Sutton Coldfield.
Jim Crowley on board Modmin on their way to winning the The Ladbrokes Supporting 'Children With Cancer UK' Novice Stakes at Goodwood Racecourse, Chichester. Jim Crowley celebrates his two thousandth UK victory in National Hunt and Flat racing
England's Tom Banton, left, fist bumps with batting partner Jonny Bairstow during the second Twenty20 cricket match between England and Pakistan, at Old Trafford in Manchester, England, Sunday, Aug. 30, 2020. (Mike Hewitt/Pool via AP)
A multi-coloured neon sign that reads "Everything Is Going To Be Alright" by Turner Prize winning artist Martin Creed has been unveiled in the grounds of Braemar Castle, Aberdeenshire. (Photo by Jane Barlow/PA Images via Getty Images)
Staff at the Ivy Victoria in London, prepare the dining area, as the government initiative Eat Out to Help Out comes to an end. (Photo by Stefan Rousseau/PA Images via Getty Images)
Benfica's head coach Jorge Jesus looks on during the pre season friendly football match between SL Benfica and AFC Bournemouth at the Luz stadium in Lisbon, Portugal on August 30, 2020. (Photo by Pedro Fiúza/NurPhoto via Getty Images)
NEWCASTLE UPON TYNE, ENGLAND - AUGUST 30: Jason Manford performs at Virgin Money Unity Arena on August 30, 2020 in Newcastle upon Tyne, England. (Photo by Thomas M Jackson/Getty Images)
AYLESBURY, ENGLAND - AUGUST 30: General view of goalmouth action during the Pre-Season Friendly between Milton Keynes Dons Women and Derby County Women at the Greenfleets Stadium on August 30, 2020 in Aylesbury, England. (Photo by Catherine Ivill/Getty Images)
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She added: "They were not just having an argument and then fighting, it was straight into fists being thrown. There was not much talking going on.
"Drinks were being dropped, bottles that they had obviously bought in the club, rings were falling off so jewellery was going everywhere, clothes were being torn.
"One of the males actually ended up with his hair being pulled out and left with a bald patch."
Police said the response would be ongoing "for some time" and urged people to stay away from the area.
The force added: "We are aware of a number of injured people, but at the moment we are not in a position to say how many or how serious.
"However, all emergency services are working together at the scene, and making sure that those who are injured receive medical care.
"Work is still going on to establish what has happened, and could take some time before we are in a position to confirm anything."