Armed police evacuated the UK’s biggest shopping district as mass panic swept through crowds hunting for discounts on Black Friday, sparking fears of a new attack.

Witnesses believe a fight on a platform at Oxford Circus tube station spread panic, leading to stampedes and rumours of gunshots, forcing police to trigger their protocol for terror attacks.

British Transport Police have appealed for information after what they described as an “altercation between two men on the platform” at Oxford Circus station. They released CCTV images of two men they would like to talk to in relation to the incident.

Screaming crowds were ordered to take shelter in shops as the station was evacuated at the start of Friday’s rush hour, but investigations have not yet found any evidence of gunfire or casualties.

The British Transport Police (BTP) said its officers received reports of shots fired on the westbound Central Line platform at Oxford Circus at 4.37pm, as passengers fled up exits towards Oxford Circus and Regent Street.

“This caused a significant level of panic which resulted in numerous calls from members of the public reporting gunfire,” a spokesperson said.

“Officers responded in line with our procedures of a terrorist incident, this included armed officers from BTP and the Metropolitan Police.

“A full and methodical search of the station and Oxford Street was conducted by our specially trained firearms officers but they did not find any evidence of gunfire at the station.”

Oxford Circus Incident – In pictures Show all 11 1 /11 Oxford Circus Incident – In pictures Oxford Circus Incident – In pictures An armed policeman runs down Oxford Street in central London on November 24, 2017, as police responded to an incident. British police said they were responding to an "incident" at Oxford Circus in central London on Friday and have evacuated the Underground station, in an area thronged with people on a busy shopping day. / AFP PHOTO / Daniel LEAL-OLIVASDANIEL LEAL-OLIVAS/AFP/Getty Images AFP/Getty Oxford Circus Incident – In pictures The scene outside the London Palladium after Oxford Circus station in London was evacuated because of an "incident". PRESS ASSOCIATION Photo. Picture date: Friday November 24, 2017. See PA story POLICE Tube. Photo credit should read: Yui Mok/PA Wire PA Oxford Circus Incident – In pictures Police set up a cordon outside Oxford Circus underground station as they respond to an incident in central London on November 24, 2017. British police said they were responding to an "incident" at Oxford Circus in central London on Friday and have evacuated the Underground station, in an area thronged with people on a busy shopping day. / AFP PHOTO / Daniel LEAL-OLIVASDANIEL LEAL-OLIVAS/AFP/Getty Images AFP/Getty Oxford Circus Incident – In pictures Oxford Circus Incident – In pictures Armed police patrol near Oxford street as they respond to an incident in central London on November 24, 2017. British police said they were responding to an "incident" at Oxford Circus in central London on Friday and have evacuated the Underground station, in an area thronged with people on a busy shopping day. / AFP PHOTO / Daniel LEAL-OLIVASDANIEL LEAL-OLIVAS/AFP/Getty Images AFP/Getty Oxford Circus Incident – In pictures LONDON, ENGLAND - NOVEMBER 24: Police set up a cordon on Regent Street and Oxford Circus underground station on November 24, 2017 in London, England. Police earlier responded to reports of an incident at London's Oxford Circus Tube station. (Photo by Jack Taylor/Getty Images) Getty Images Oxford Circus Incident – In pictures epa06348638 London police officers react to an incident near Oxford Circus tube station in Oxford Street, central London, Britain. 24 November 2017. The London Metropolitan Police (MPS) state that Police officers are continuing to search the area and to date police have not located any trace of any suspects, evidence of shots fired or casualties. Officers continue to work with colleagues from British Transport Police in the area of Oxford Circus. EPA/FACUNDO ARRIZABALAGA EPA Oxford Circus Incident – In pictures epa06348637 Armed London police officers react to an incident near Oxford Circus tube station in Oxford Street, central London, Britain. 24 November 2017. The London Metropolitan Police (MPS) state that Police officers are continuing to search the area and to date police have not located any trace of any suspects, evidence of shots fired or casualties. Officers continue to work with colleagues from British Transport Police in the area of Oxford Circus. EPA/FACUNDO ARRIZABALAGA EPA Oxford Circus Incident – In pictures epa06348653 London police officers react to an incident near Oxford Circus tube station in Oxford Street, central London, Britain, 24 November 2017. The London Metropolitan Police (MPS) state that Police officers are continuing to search the area and to date police have not located any trace of any suspects, evidence of shots fired or casualties. Officers continue to work with colleagues from British Transport Police in the area of Oxford Circus. EPA/FACUNDO ARRIZABALAGA EPA Oxford Circus Incident – In pictures A policeman sits with a couple of shoppers in a coffee shop in Regent Street in central London on November 24, 2017, as police responded to an incident. British police said they were responding to an "incident" at Oxford Circus in central London on Friday and have evacuated the Underground station, in an area thronged with people on a busy shopping day. / AFP PHOTO / Daniel LEAL-OLIVASDANIEL LEAL-OLIVAS/AFP/Getty Images AFP/Getty Images Oxford Circus Incident – In pictures epa06348642 London police officers react to an incident near Oxford Circus tube station in Oxford Street, central London, Britain. 24 November 2017. The London Metropolitan Police (MPS) state that Police officers are continuing to search the area and to date police have not located any trace of any suspects, evidence of shots fired or casualties. Officers continue to work with colleagues from British Transport Police in the area of Oxford Circus. EPA/FACUNDO ARRIZABALAGA EPA

As the cause of the alert remained unconfirmed, several high-profile figures were condemned for spreading incorrect information on social media.

Former EDL leader Tommy Robinson deleted a tweet on “what looks like another jihad attack”, while singer Olly Murs reported baseless rumours of gunshots inside Selfridges while it was being evacuated as a precaution, and Sky News presenter Kay Burley repeated false claims of a “man with a gun”.

Passengers on the platform at the time claimed the panic was started by a fight between two men, describing how the evacuation order was prompted by a member of the public pushing an emergency button.

Regan Warner said she saw a man bumping into another man on the “overcrowded platform” at 4.35pm.

“They exchanged words, then a punch to the gut, then a full-out fight,” she added.

“People were trying to break it up, there was lots of yelling. People were running away, a woman fainted, children were scared and crying.

“The emergency button was pressed. The fight was broken up and the parties walked in opposite directions.”

She jumped on a departing Tube train, hearing an announcement being given out over the station announcement system ordering a full evacuation as it departed.

The Met responded to the incident as though it was a full-blown terror attack (AFP/Getty)

Ms Warner’s account was echoed by a Twitter user called Annabel, who described how “crying and screaming” around the fight spread panic, which was compounded by thousands of people fleeing to street level.

“It turned into a stampede in rush hour on Black Friday … Terrifying the street and then rumours as usual spread, and caused even more fear,” she wrote.

Another witness, Lysi P, said mass panic started after the evacuation announcement went out, adding: “As the speakers went off I saw everyone run from the platform – therefore I can only assume that people panicked.”

Ryan Butcher, a reporter for The Independent who was in another part of the station at the time, said the announcement told everyone to evacuate because of “a reported emergency”.

“I just heard screams, someone shouted 'run’,” he added. “People started falling over in the streets. I saw everyone running into buildings so I went into the nearest one.”

Mr Butcher was sheltering in a nearby restaurant, where he said other people were “shaking and crying”, adding: “It's just terrifying.”

He was later allowed to leave by police officers, who were lifting security cordons in the area as searches for the cause of the alarm continued.

Police said they had responded “as if the incident was terrorism” because of the nature and number of 999 calls from different locations in the Tube station and above ground around Oxford Street.

“The first armed response vehicle was on the scene in less than one minute from receiving our first call,” a spokesperson for the Metropolitan Police said after the incident was stood down.

“Officers working with colleagues from BTP carried out an urgent search of the area. No causalities, evidence of any shots fired or any suspects were located by police.”

BTP said it had received no reports of casualties apart from one woman who “sustained a minor injury when leaving Oxford Circus station”.

“We understand that incidents like this cause panic and concern,” a spokesperson added.

“We would therefore like to thank Londoners for their patience during this incident. Our officers will remain highly visible on duty this evening to reassure the public.”

The London Fire Brigade said it had sent three fire engines and 15 firefighters to the scene.

Both Oxford Circus and Bond Street station were closed during the alert but have since been reopened, with events including the Royal Variety Performance at the nearby London Palladium going ahead as planned.

Black Friday brought fewer shoppers than initially expected to Oxford Street, with television footage showing a solitary man entering an electrical shop for its special early opening.

The area has been identified among many potential “soft targets” for terror attacks in London, as Isis advises its supporters to target crowds with vehicles, knives or guns in areas lacking security.

The incident came two months after a bomb partially exploded on a tube train at Parsons Green station in a suspected Isis-linked terror attack.

An 18-year-old Iraqi refugee, Ahmed Hassan, has been charged with attempted murder and explosives offences.

Oxford Circus was previously evacuated in August after a small fire caused by an electrical fault on a Bakerloo Line train.

Two people were taken to hospital for smoke inhalation in the incident, which is under investigation.

There were additional fears of a terror attack in South Kensington, where a car hit pedestrians near the Natural History Museum last month, but police confirmed the collision was an accident.

Five terror attacks have struck the UK so far this year, killing more than 30 people and injuring hundreds, while eight plots have been foiled since the Westminster massacre in March.