Footage has emerged of the immediate aftermath of an explosion in the St Petersburg metro system.
At least 9 people have been killed and 50 more injured according to local media reports.
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 as saying at least one of the blasts involved a device filled with shrapnel.
The Governor's press office said 9 have died and a further 50 have been injured.
Andrey Kibitov, the head of the city governor's press service, said fifty people were injured in the blasts 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.
"I have already spoken to the head of our special services, they are working to ascertain the cause," the president said, at a meeting with Belarus President Alexander Lukashenko.
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