Blast in Russian Metro station kills 10

Authorities closed all St Petersburg metro stations

Ten people were killed and more than 20 were injured when an explosion tore through a train carriage in a St Petersburg metro tunnel on Monday in what authorities called a probable terrorist attack.

Russian news media reported that police were searching for a man recorded on surveillance cameras who was thought to have been involved in the attack, which coincided with a visit to the city by President Vladimir Putin.

A grainy photograph published by the Fontanka news outlet showed a middle-aged man with beard and black hat. Interfax news agency cited unnamed sources as saying the bomb, packed with shrapnel,