Otkrytaya Rossiya news outlet reports that there were two explosions: the first blast rocked the Technological Institute station while the second one occurred between Sennaya and Technological Institute stations.
Russian Interfax confirmed that both blasts with a total yield of 200-300 grams of TNT equivalent took place in a car.
According to Gazeta.ru and RBC, at least 10 people were killed. TASS news agency reports that an unidentified explosive device was triggered in the car.
The image posted on the social media show the twisted door of the car and passengers lying on the floor.
Nevsky Prospekt, Mayakovskaya, Ploschad Vosstaniya, Sadovaya, and Technological University metro stations are currently closed.