The explosion at a supermarket in Russia's second-largest city on Wednesday was a terrorist attack, President Vladimir Putin said, adding that another attack had recently been thwarted.

Russian President Vladimir Putin delivers a speech during a state awards ceremony for military personnel who served in Syria, at the Kremlin in Moscow, Russia, December 28, 2017.
Russian President Vladimir Putin delivers a speech during a state awards ceremony for military personnel who served in Syria, at the Kremlin in Moscow, Russia, December 28, 2017. ( Reuters )

A bomb blast in a St Petersburg supermarket on Wednesday was an act of terrorism, Russian President Vladimir Putin said on Thursday, adding that security forces whose lives were threatened by suspected terrorists should shoot to kill if necessary.

At least 13 people were injured when an improvised explosive device went off at a storage area for customers' bags at the supermarket in Russia's second-largest city St Petersburg. 

Putin was speaking on Thursday at an awards ceremony in the Kremlin for Russian personnel who served in Syria.

"You know that yesterday in St Petersburg a terrorist act was carried out," Putin told the audience, referring to the explosion.

Investigators have opened a criminal case into Wednesday evening's blast, which they said was caused by a homemade bomb packed with pieces of metal.

No one has claimed responsibility for the attack.

Russian media reports said the bomb was hidden in a locker where shoppers leave their belongings.

Another attack prevented

Federal police (FSB) had recently prevented "another attempted terrorist act," Putin also said.

The Russian president did not give details, but the Kremlin said earlier this month that a US tip-off had helped thwart a planned attack on St Petersburg's Kazansky Cathedral.

Putin added that the security situation in Russia would be much worse if thousands of Russian citizens who fought with Daesh in Syria had been allowed to return home.

Putin said security forces should take no chances with their own lives if confronted by suspected terrorists.

"I yesterday ordered the FSB director to act within the framework of the law when detaining these bandits of course, but if there is a threat to the life and well-being of our employees ... to act decisively, not take any prisoners, and liquidate the bandits on the spot."

Source: TRTWorld and agencies