Passengers on the southbound Victoria Line train reported seeing and smelling smoke in the packed carriages at about 1730 BST.

It is thought the smell was noticeable from Euston underground station, becoming worse as it reached Warren Street station where a number of passengers tried to get out.

By the time the train reached Oxford Circus, thick black smoke was filling a number of carriages towards the front of the train.

The train was evacuated and commuters pushed passed each other as they tried to leave the platform and get to the escalators.

The entire Oxford Circus station was then evacuated and the fire brigade called.

A London Underground spokeswoman said there had not been a fire.

The smoke was caused by a defect in the train's brakes, she said.

The train was moved to Victoria station to be repaired.