Updated at 22:14
Russia's National Anti-Terrorism Committee has confirmed that at least 11 people have died in explosions on the St Petersburg subway system.
Reports in Russia said there were blasts on a train between two underground stations.
The device was reportedly filled with shrapnel and Russia Today has reported that at least 50 people have been injured:
URGENT: 50 injured in #SaintPetersburg metro #blast - Governor's press secretary https://t.co/CIhbXmoopD pic.twitter.com/3oY3mcE9lx
— RT (@RT_com) April 3, 2017
Earlier it was reported that two blasts had occurred and ten people had died.
Russia's Anti-Terrorism Committee has now said that nine people died and 20 have been injured.
The Russian Prosecutors Office has called it a terror attack.
The Anti-Terror committee also confirmed that a second device was found and has been deactivated.
Pictures have emerged on social media of people lying on a platform following the blast.
All metro stations throughout the city have now been closed.
Kremlin spokesman Dmitry Peskov said the Russian President Vladimir Putin - who was due to visit the city today - has been informed about the explosion.
The president has expressed his condolences to the families of the victims, saying: "I have already spoken to the head of our special services, they are working to ascertain the cause (of the blasts)."
He said authorities are considering all possible causes for the explosion - including terrorism.
Sky's News correspondent John Sparks is in Russia:
The St Petersburg underground railway said in a statement: "An evacuation from the stations is ongoing, there are people injured.
"An unidentified object supposedly blew up in a (train) carriage."
The explosion took place in a tunnel between two metro stations, Russian state media reports, citing officials.
The blast occurred in a metro car that was traveling in the tunnel between the Sennaya Ploschad [square] and Tekhnologichesky Institute stations.
The St Petersburg Metro is made up of five lives and 67 stations. Opened in November 1955, it transports 2.3 million people a day and has more than 1,600 train cars.
All travel on city transport will be free of charge for the rest of Monday, St. Petersburg Transport tweeted.
