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"Officers are responding to reports of an incident at Oxford Circus station," British Transport Police said on Twitter. "The station is currently closed, please avoid the area at this time," they said.
Transport for London said: "Oxford Circus Station is closed while we investigate a customer incident."
A Metropolitan Police spokesman contacted by AFP said the details of the incident were not known yet.
Oxford Circus station is in the heart of London's shopping district, which is particularly busy because of stores offering Black Friday discounts.
People were seen running from the scene, the BBC reported.