Police said in a statement: "Police have responded as if the incident is terrorist related".
Oxford Circus tube station was evacuated following a "customers incident". "Avoid area if possible".
Armed police run along Oxford Street, London, Britain November 24, 2017.
British Transport Police (BTP) received reports at 4.37pm of gunfire on the westbound Central Line platform.
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The Metropolitan Police tweeted they have not located "any trace of suspects, evidence of shots fired or casualties". "Officers are on scene, more information when we get it".
Armed police have arrived on the scene to handle the situation after a gunman was reported to be firing shots. They gave no details on what happened, but crowds were seen running down Oxford Street, a shopping strip usually busy with pedestrians and heavy traffic.
Transit authorities say the station has been evacuated and trains are not stopping there. It was a very panicked scene.
"A police presence remains in the area to support the public".