Oxford Circus tube station has been evacuated amid reports of smoke billowing from a train.
The smoke was reportedly caused after a Bakerloo Line tube caught fire.
Pictures on social media show smoke issuing from a train at a platform, while bystanders cover their faces to avoid inhaling it.
The authorities responded to a fire alert, and the London Fire Brigade, as well as the British Transport Police, raced to the scene.
Transport for London's website has reported service on the Bakerloo Line to be partly suspended between Elephant and Castle to Piccadilly Circus while the situation is dealt with.
It has advised commuters to seek different travel routes.