Twin explosions hit the subway in Russia's second largest city St. Petersburg on Monday, with at least 10 people reportedly killed, 50 others injured in the incident.
"According to the first preliminary data, around ten people were killed," an emergency source told Russian news agencies after the Saint Petersburg metro said that an unidentified object had blown up in a train carriage.
Initial footage circulated from the blast scene showed blown-up doors of a metro train in a station.
A homemade bomb containing shrapnel is believed to have caused a deadly explosion on an underground train in the Russian city of St Petersburg, state news agency RIA Novosti reported.
Another unexploded device has been found on the St Petersburg metro system, several Russian agencies reported.
"A bomb that failed to go off was found at Vosstanaya Square metro station," Interfax said citing an anonymous source, whereas police did not confirmed the report.
The St. Petersburg metro has shut down all stations due to the deadly train explosion.
Kremlin spokesman Dmitry Peskov told reporters that President Vladimir Putin has been told of the explosion.
"Yes, the president was informed about this," Peskov said, according to TASS.
Meanwhile, Russian President Vladimir Putin, who was visiting the city on an unrelated trip, said that Russia is considering all causes, including terrorism regarding the attack. He offered his condolences to the families of those killed.
Russia's National Anti-Terrorist Committee said an unidentified explosive device went off on a train that was traveling between two stations. Maxim Liksutov, Moscow's deputy mayor, told Interfax that Moscow authorities were tightening security on the subway in the Russian capital.
The agency that runs the subway said several stations in the northern Russian city were closed and that an evacuation was underway.
Social media users posted photographs and video from a subway station in the city center, showing people lying on the floor outside a train with a mangled door. Frantic commuters reached into doors and windows, trying to see if anyone was there and shouting "Call an ambulance!" The explosion happened between Sennaya Ploshchad and Tekhnologichesky Institut stations.
Russia's National Anti-Terrorism Committee said that security will be tightened at all critical transport facilities after the deadly blast.
