10 people were killed Monday in a blast on the metro system of Russia's second city Saint Petersburg.
According to the first preliminary data, around ten people were killed, after the Saint Petersburg metro said that an unidentified object had blown up in a train carriage.
The Tass and Interfax agencies reported the blast hit at the Sennaya Ploshchad metro station, which left a number of victims.
Images posted on social media showed a train carriage with its doors blown out and damage inside.
Russian President Vladimir Putin, who is in the city, has been informed, Russian media say.
The cause of the explosion is not yet known. Russian news agencies said there may have been two blasts, with a second at the nearby Institute of Technology station.
Meanwhile the explosion hit the metro system of Russia's second city Saint Petersburg on Monday, the firm running it said, after an unidentified object blew up in a train.
"An evacuation from the stations is ongoing, there are people injured," the Saint Petersburg metro said in a statement carried by Russian news agencies. "An unidentified object supposedly blew up in a (train) carriage."