Scotland Yard said police responded "as if the incident is terrorist related".
There were reports of people running out of the Tube station on Friday afternoon.
Met Police advised those who are on Oxford Street to go into a building and to "stay inside until further direction".
The capital's transport operator, Transport for London, said trains were not stopping at the station due to the unspecified incident.
Oxford Circus tube station was evacuated following a "customers incident".
British Transport Police tweeted just after 4:40 p.m. that officers were are on the scene.
The station, located on Oxford Street which is a destination for shoppers on Black Friday, has been evacuated, according to eyewitness reports.
The reports sparked panic in the area around one of London's busiest subway stations. Local residents said heavy police presence could be seen.
The attacks killed 35 people and wounded dozens more.
The two London underground stations in the heart of the city, Oxford Circus and Bond Street, which had been shut down have now reopened and the area seems to be returning to normality.