Two explosions on a train in a metro station in St Petersburg have injured several people, local media reports.
At least 10 people were injured, the RIA news agency reports, while Interfax reported there appear to have been two explosions.
The blast involved a device filled with shrapnel, Interfax cited a source as saying.
Russian President Vladimir Putin has been informed, according to RIA.
The Life News website, a news outlet with close ties to Russia’s security services, showed pictures of blown-out train doors and injured people on the station platform.
Local media also report three metro stations are closed.
Witnesses told Reuters there were eight ambulances near St Petersburg’s Sennaya Ploshchad metro station.