At least 10 people have been killed and 50 more injured in explosions in the St Petersburg metro system.
There were blasts in two metro carriages at two stations, St Petersburg emergency services said.
News agency Interfax cited a source as saying at least one of the blasts was caused by a bomb filled with shrapnel.
Fifty people were injured in the blasts, Andrey Kibitov, the head of the city governor's press service said on Twitter.
Seventeen ambulances are currently treating the injured, Mr Kibitov added.
A Reuters witness saw eight ambulances near the Sennaya Ploshchad metro station while local media reported the nearby Institute of Technology station was also affected.
Russia's Anti-Terrorist Committee confirmed at least 10 people had been killed.
It said an unidentified explosive device went off on a train travelling between two stations.
All metro stations in St Petersburg have been closed, Interfax reported, citing metro staff.