At least 10 people have been killed in a blast at the St Petersburg Metro, according to various media reports.

Many more have been injured in what is believed to be two separate blasts on a Metro train in St Petersburgh, Russia, the BBC and Daily Telegraph reported.

Pictures posted on the Internet showed a train with twisted and buckled doors, and people lying on the station platform, apparently seriously injured.

The blasts took place at Sennaya Ploshchad station and the nearby Institute of Technology station, Russian media reported.

A number of stations were immediately closed by security forces and passengers evacuated, according to Russian media.

Russian President Vladimir Putin was in St Petersburgh at the time of the incident, and is being kept informed, Tass News Agency reported.