Up to nine people have been injured by an explosion at a supermarket in St Petersburg, Russian officials said.
The Investigative Committee, the nation's top investigative agency, said a device containing 200 grams (7 ounces) of explosives went off at a storage area for customers' bags.
Initial reports suggests the explosive TNT was used in the attack.
No one has claimed responsibility for the explosion at the Perekrestok supermarket in the city's northwest Kalininsky district.
The Investigative Committee said the blast injured four people, while St. Petersburg officials said there were nine injured.
A criminal investigation has been launched.
Alexander Klaus, the head of St Petersburg's investigative committee, said: "All possible versions of what has happened are being worked on.
"As of now, it has been established that 10 people were taken to the city's hospitals with injuries. At the moment, the lives of those injured are not under threat."
Russian President Vladimir Putin telephoned US President Donald Trump earlier this month to thank him for a CIA tip that helped thwart a series of bombings in St. Petersburg earlier this month. The Federal Security Service, or FSB, said seven suspects linked to the Islamic State group were arrested in connection to the alleged plot.
The Kremlin said the arrested suspects had planned to bomb St. Petersburg's Kazan Cathedral and other crowded sites.
In April, a suicide bombing in the St. Petersburg's subway left 16 people dead and wounded more than 50.
AP
