Moscow (CNN) More than a dozen people were injured in an explosion at a St. Petersburg supermarket Wednesday, according to Russian state media.

President Vladimir Putin called the blast a "terror attack" during an address to military officers Thursday in Moscow, calling for a full investigation.

Preliminary data shows that an explosive device found at the scene contained 200 grams (7 ounces) of TNT, state-run RIA news agency reported. The device was inside a locker at a chain supermarket called Perekrestok, located in an entertainment complex.

Firefighters respond to the blast at the Perekrestok supermarket in Kalinina Square.

Tass reported that the Investigative Committee of the Russian Federation has opened a criminal investigation into the explosion, citing Svetlana Petrenko, an official representative for the committee.

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