An injured person is helped by emergency services outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg, Russia April 3, 2017. REUTERS/Anton Vaganov (credit:Stringer . / Reuters)
RUSSIA-BLAST/METRO(02 of10)
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An injured person is helped by emergency services outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg, Russia April 3, 2017. REUTERS/Anton Vaganov (credit:Stringer . / Reuters)
RUSSIA-BLAST/METRO(03 of10)
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Emergency services direct pedestrians outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg, Russia April 3, 2017. REUTERS/Anton Vaganov (credit:Stringer . / Reuters)
RUSSIA-BLAST/METRO(04 of10)
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An injured person is helped by emergency services outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg, Russia April 3, 2017. REUTERS/Anton Vaganov (credit:Stringer . / Reuters)
RUSSIA-BLAST/METRO(05 of10)
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An injured person stands outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg, Russia April 3, 2017. REUTERS/Anton Vaganov (credit:Stringer . / Reuters)
Explosion rips through St Petersburg Underground train(06 of10)
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ST PETERSBURG, RUSSIA -- APRIL 3, 2017: Fire fighters at the entrance to Sennaya Ploshchad station of the St Petersburg metro in the aftermath of an explosion which occurred in a train at 14:40 Moscow time; according to Russian National Antiterrorism Committee several people were killed in the explosion. Sergei Konkov/TASS (Photo by Sergei Konkov\\TASS via Getty Images) (credit:Sergei Konkov via Getty Images)
Explosion rips through St Petersburg Underground train(07 of10)
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ST PETERSBURG, RUSSIA -- APRIL 3, 2017: Emergency service vehicles at the entrance to Tekhnologichesky Institut station of the St Petersburg metro in the aftermath of an explosion which occurred in a train at 14:40 Moscow time; according to Russian National Antiterrorism Committee several people were killed in the explosion. Sergei Konkov/TASS (Photo by Sergei Konkov\\TASS via Getty Images) (credit:Sergei Konkov via Getty Images)
Explosion rips through St Petersburg Underground train(08 of10)
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ST PETERSBURG, RUSSIA -- APRIL 3, 2017: Fire fighters and ambulances at the entrance to Sennaya Ploshchad station of the St Petersburg metro in the aftermath of an explosion which occurred in a train at 14:40 Moscow time; according to Russian National Antiterrorism Committee several people were killed in the explosion. Sergei Konkov/TASS (Photo by Sergei Konkov\\TASS via Getty Images) (credit:Sergei Konkov via Getty Images)
Explosion at a subway station in St Petersburg(09 of10)
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SAINT-PETERSBURG, RUSSIA - APRIL 3: Health team workers are dispatched after an explosion at a subway station in St Petersburg, Russia on April 3, 2017. At least 10 people were killed on the blast. (Photo by Sergey Mihailicenko/Anadolu Agency/Getty Images) (credit:Anadolu Agency via Getty Images)
RUSSIA-BLAST/METRO(10 of10)
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An injured person is helped by emergency services outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg, Russia April 3, 2017. REUTERS/Anton Vaganov (credit:Stringer . / Reuters)