According to preliminary reports, ten people were killed by an explosion inside a metro train at the Sennaya Square station in St. Petersburg, emergency services told TASS.
"According to information available at this point ten people died. Others were injured," a source said adding that the number of casualties was still to be specified. TASS has no official confirmation at this point.
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Evacuation is under way at a blast-hit subway station. Seven metro stations in the city have been closed following the blast.
"Park Pobedy, Elektrosila, Moskovskiye Vorota, Frunzenskaya, Tekhnologichesky Institut, Sennaya Ploshchad and Gostiny Dvor metro stations have been closed," the metro's press service reports.
A spokesman for the regional department of Russia’s Emergencies Ministry said it was checking reports of the smoke in the metro. "There is a complaint about the smoke, the staff members are going to the scene," he said.