Explosion injures several at supermarket in St. Petersburg, Russia

Reuters/Anton Vaganov

A policeman stands guard near a supermarket after an explosion in St Petersburg, Russia December 27, 2017.

• At least four people were injured in St. Petersburg, Russia, on Wednesday after an explosion at a supermarket.
• Investigators said the explosives were inside a locker in the supermarket meant to store customers' bags.
• Russian authorities are investigating the incident as an attempted murder.

At least four people were injured Wednesday 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 7 ounces of explosives went off inside a locker in a storage area for customers' bags.

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 and authorities suspect the incident was attempted murder.

"All possible versions of what has happened are being worked on," Alexander Klaus, the head of St Petersburg's investigative committee, told Reuters. "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. 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.