A large fire has broken out in a railway arch in south London, the British capital's fire brigade said on Monday, diverting trains and sending plumes of black smoke billowing into the sky.

Video footage on the London Fire Brigade's Twitter site showed an explosion and a ball of fire coming from the archway, with a warning for people to avoid the area.

Police said the incident was not terror-related. There were no immediate reports of anyone being injured.

The London Fire Brigade (LFB) said 10 fire engines and 70 firefighters were tackling the blaze, which broke out in one of the archways near the Elephant and Castle area of south London.