Putin says St. Petersburg market explosion was 'terror attack'

An explosion at a supermarket in St. Petersburg on Wednesday that injured 13 people was a terrorist attack, Russian President Vladimir Putin said Thursday.

Putin's announcement came despite reluctance by Russian law enforcement agencies to describe the explosion as such.

Officials said a device detonated in a storage area of a supermarket in Russia’s second-largest city.

The device contained 7 ounces of explosives and was rigged with shrapnel to cause more damage, investigators added.

The president, speaking during a military awards ceremony, said he told the director of the country’s Federal Security Service, “while arresting these bandits, to act, obviously only within the limits of the law.

“But if the lives or health of our employees and our officers are threatened — to act decisively, to take no prisoners, to liquidate the bandits on the spot,” Putin added.

PUTIN SAYS RUSSIA'S SPY AGENCIES PREVENTED 60 TERROR ATTACKS

Putin's spokesman, Dmitry Peskov, would not offer any specifics on what led Putin to declare the attack an act of terrorism, but said  the shrapnel that was part of the explosive device proved the explosion "was a terror attack anyway."

People walk past the scene of an explosion at a supermarket in St. Petersburg, Russia, Thursday, Dec. 28, 2017.  Russian President Vladimir Putin says Wednesday's explosion at a supermarket in the country's second-largest city was a terrorist attack, at least 13 people were injured. (AP Photo/Dmitri Lovetsky)

Putin said Wednesday's supermarket explosion that left at least 13 people injured was a terrorist attack.  (AP Photo/Dmitri Lovetsky)

No one has yet claimed responsibility for Wednesday’s supermarket attack, and eight of the injured were still hospitalized.

Putin, speaking at a military awards ceremony Thursday, also addressed the U.S. government’s help in thwarting a planned terror attack — also in St. Petersburg.

SYRIAN CAMPAIGN SHOWCASED RUSSIAN MILITARY MIGHT, PUTIN SAYS

Information provided to the Kremlin by the CIA was sufficient enough to track down and detain seven suspects connected to ISIS who were planning to bomb the Kazan Cathedral and other locations.

A suicide bombing attack in a St. Petersburg subway in April left 11 people dead and more than 50 others wounded.

The Associated Press contributed to this report.

Nicole Darrah covers breaking and trending news for FoxNews.com. Follow her on Twitter @nicoledarrah.