Reuters witness said area around the station had been cleared of people and traffic
Metropolitan Policesaid that its officers had "responded as if the incident is terrorist related".
In a statement, police said they had received "numerous" calls reporting shots fired in the Oxford St area, crammed with shoppers for the Black Friday sale.
About an hour after the first report of shots, the Metropolitan Police force said officers "have not located any trace of any suspects, evidence of shots fired or causalities". The area is a crowded shopping district in the center of the city.
Footage by one eyewitnesses shows people running down a street.
"We continue to respond to an incident at Oxford Circus", the British Transport Police said in a statement.
On the Oxford Circus Station, people left in panic after hearing a loud firing voice.
Authorities believe the two men had some type of confrontation on the Oxford Circus subway platform Friday afternoon, sparking panicky, false reports that guns had been fired.
Sky News reported Bond Street and Oxford Circus tube stations were close but have since been reopened. Police everywhere!' he's tweeted.
No casualties have been reported at this stage. People were climbing on top of each other.
British Transport Police had released photos of the two men on Friday night and appealed for information about the incident. It was briefly at the highest level, "critical" in September after a bomb partially detonated on a subway train in London, and in May, following the bombing at an Ariana Grande concert in Manchester that killed 23 people.
The UK's terrorism threat level is now at "severe", the second-highest level on a five-step scale.
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