A homemade bomb blast at a supermarket in the Russian city of Saint Petersburg injured 10 people on Wednesday, officials said, sparking a probe into attempted murder.

"According to preliminary information, an explosion of an unidentified object occurred in a store," a spokeswoman for Russia's Investigative Committee, Svetlana Petrenko, said in a statement.

The blast was caused by a "homemade explosive device with the power equivalent to 200 grammes of TNT filled with lethal fragments," she said.

"The investigation is looking at all possible causes of what happened," she said, adding that a probe for attempted murder had been launched.

The incident comes several months after Russia's second city was rocked with a metro bombing in April which killed 16 people.

"Ten people have been hospitalised, their lives are not in danger," the head of Saint Petersburg investigative unit Alexander Klaus told Russian news agencies.

An emergencies ministry representative told AFP that one of the injured was in serious condition.

An AFP correspondent at the scene observed first responders and police as well as a car belonging the Federal Security Service (FSB), which investigates acts of terror.

The building containing the supermarket did not appear to have sustained serious damage.