Footage has emerged of the immediate aftermath of an explosion in the St Petersburg metro system.

Ten people have been killed and 50 more injured in the explosion.

Video footage shows crowds of people pacing around the station looking scared in the immediate aftermath of the blast.

Passengers can be heard shouting and seen peering into the train carriages to decipher what is going on. The train carriage doors appear visibly mangled and blown out from the blast.

There was only one blast in St Peterburg's metro system which happened in a train in between two stations, a source in Russia's emergency services said on Monday.

"There was one blast in one site in between (stations) as the train arrived at the Technology Institute station from Sennaya (Ploshchad) station," the source told Reuters.

Russian media reported earlier that there were two blasts.

News agency Interfax cited a source saying the blast was caused by a bomb filled with shrapnel.

The Governor's press office said 9 have died and a further 50 have been injured.

St. Petersburg metro blast Show all 5 1 /5 St. Petersburg metro blast St. Petersburg metro blast An injured person is helped by emergency services outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg Reuters St. Petersburg metro blast Emergency services work outside Sennaya Square metro station in St Petersburg Reuters St. Petersburg metro blast An injured person is helped by emergency services outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg Reuters St. Petersburg metro blast Emergency services direct pedestrians outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg Reuters St. Petersburg metro blast Twitter/ varlamov

Andrey Kibitov, the head of the city governor's press service, said fifty people were injured in the blast on Twitter.

Interfax reported that all metro stations in St Petersburg have been closed.

Russian President Vladimir Putin is aware of the blast and has said investigators are looking into a possible terror attack and other theories for the subway explosion.

Mr Putin was in St Petersburg earlier on Monday but is now outside the city, according to his spokesman Dmitry Peskov.