Blast in Russia's Saint Petersburg injures four: officials
"According to preliminary information, an explosion of an unidentified object occurred in a store," Investigative Committee spokeswoman Svetlana Petrenko said in a statement.
"Four people have been hospitalised."
She said the incident has been classed as attempted murder, without mentioning terrorism as a possible cause.
Police said the blast occurred in a supermarket northeast of the city centre, with sources telling Russian agencies that the exploding object was traced to a storage locker.
"About 6.30pm there was the sound of a blast. As a result, several people have been injured," the Saint Petersburg police said, giving the incident's location.
"There is no fire. All shoppers have been evacuated," an emergencies ministry representative told Interfax, adding that police and investigators were at the scene.