Hundreds of shoppers in London's most famous shopping street have been seen running away in panic after Oxford Circus underground station was evacuated.
Despite reports, police say there is no evidence of shots being fired or any casualties.
There was a "significant level of panic" on Oxford Street and at Oxford Circus Tube station as witnesses said they heard shots.
But after armed police responded to the area which was packed with Black Friday shoppers and rush-hour commuters, they announced nothing had been found and the Tube station has re-opened. One woman suffered minor injuries in the crush as the station was evacuated.
In a statement British Transport Police said: "At 4.37pm this afternoon, officers were called to Oxford Circus station following reports of gunfire on the westbound Central Line platform.
"Passengers at the station then self-evacuated the station onto Oxford Circus and Regent Street area of London.
"This caused a significant level of panic which resulted in numerous calls from members of the public reporting gunfire.
"Officers responded in line with our procedures of a terrorist incident; this included armed officers from British Transport Police and the Metropolitan Police. A full and methodical search of the station and Oxford Street was conducted by officers.
"At this stage, we are examining the circumstances of the incident which resulted in the station being evacuated.
"During the station evacuation, one woman is believed to have sustained a minor injury."
Scotland Yard treated the incident as a potential "terror incident".
Daily Mail journalist Keiligh Baker was there as the incident unfolded: "Lots of armed police arrived and stormed Oxford Street. They were shouting 'move, move, move!'.
"Then the uniformed officers started shouting 'go, go, go'. People were sprinting and screaming."
The singer Olly Murs has also claimed on Twitter he is in Selfridges and that there are reports of "gun shots".
A video posted online by Twitter user Charlotte Terry appears to show hundreds of people leaving the area around the underground station, as police quickly secure the area.
Greg Owen, 37, from London, said: "I was next to the tube station and everyone started screaming and shouting and then a flood of people came up the stairs."
And a witness who only wanted to be known as Emma said she heard something which sounded like "three shots."
She said: "There were shots fired on Oxford Street and then armed police ran into me and my friend.
"Armed Police were running up Argyll Street and now we're locked in French Connection."
Earlier reports of gunshots at Selfridges are thought to have been a false alarm, according to a security guard speaking to The Telegraph.
The panic is believed to have spread by rumours of a gunman inside. The shop has now been evacuated.
A Telegraph employee was shopping in John Lewis with her daughters when there was a sudden stampede for the doors and people screaming amongst reports of gunshots.
The trio were ushered into the the basement of a chemist around the corner from Oxford Street, along with scores of other shoppers.
"We were in the women's section on the second floor when there was loads of screaming and a mass stampede," she said.
"People we are with said they had heard gunshots."
Oxford Circus remains closed while Bond Street station has also been shut to prevent overcrowding.
Hundreds of people are being directed down Bond Street away from the area.