Russian President Vladimir Putin has said a blast that injured at least 10 people at a St. Petersburg supermarket was a terrorist act, and urged security forces to "take no prisoners" when dealing with imminent threats from terror-plot suspects.
Talking tough on December 28, a day after the explosion of what authorities said was a makeshift bomb packed with metal fragments, Putin said law enforcement officers should "liquidate" suspected terrorists if they pose a potentially deadly threat.
"You know that a terrorist act was carried out in St. Petersburg yesterday," Putin said at a medals ceremony in the Kremlin for military personnel who have taken part in Russian operations in Syria.
Investigative Committee spokeswoman Svetlana Petrenko said on December 27 that the "homemade bomb" that ripped through a customer locker area at a Perekryostok supermarket exploded with the power equivalent to 200 grams of TNT.
But law enforcement authorities initially opened an investigation on suspicion of attempted murder, seeming to suggest that terrorist motives were not suspected.
Russia calls its military campaign in support of Syrian government forces a "counterterrorism operation," and Putin suggested that soldiers who served in Syria had helped avert potential attacks by killing extremists and preventing them from returning to Russia.
"What would happen if these thousands...returned to our country -- returned trained, armed, and well prepared?" he said at the ceremony, referring to Russians who have traveled to Syria to fight alongside Islamic State (IS) and other extremist groups.
He said he had ordered the head of the Federal Security Service (FSB) a day earlier to tell his officers to act decisively to when dealing with suspected terrorists.
FSB officers should act "within the framework of the law" when detaining "these bandits," he said. "But if there is a threat to the life and health of our officers, [they should] act decisively -- take no prisoners, and liquidate the bandits on the spot."
Officials said late on December 27 that nine of the 10 injured in the blast had been sent to the hospital for treatment. At least one person was in serious condition and one other had been released.
The blast comes after the FSB said on December 15 that it had arrested seven suspected Islamic extremists who were planning to carry out bomb attacks on a church and other crowded places in St. Petersburg the following day.
The FSB said the arrestees were suspected members of IS and that they were being directed from abroad via the messaging app Telegram.
After the arrests, Putin telephoned U.S. President Donald Trump to thank him for what Russian officials said was a CIA tip that helped prevent the bombings in St. Petersburg, which is Putin's hometown and a popular tourist destination.
Putin mentioned the alleged December 16 terror plot in his comments on December 27, saying that the FSB had "very recently averted another attempted terrorist act" in the city.
Russia has been plagued for more than two decades by terrorist attacks that in many cases have been linked to the two post-Soviet separatist wars in Chechnya and the subsequent Islamist insurgency in the North Caucasus.
There have been fewer attacks in St. Petersburg than in Moscow, but an explosion that officials said was set off by a Kyrgyz-born, ethnic Uzbek suicide bomber killed 16 people on a St. Petersburg subway car in April.
The authorities are heightening security in St. Petersburg and other cities that are to host 2018 World Cup soccer matches from June 14 to July 15.
The supermarket bombing also came less than three months before a March 18 presidential election that appears certain to hand Putin a new six-year term.
On December 12, the FSB said it had arrested three suspected members of what it said was an extremist "cell" directed by IS that was planning terror attacks in Moscow during the New Year holidays and the presidential campaign.
The FSB frequently announces that it has foiled terrorist plots ahead of holidays and important events. It was impossible to independently verify the agency's statements about the alleged plans for attacks in Moscow and St. Petersburg.
Russia has backed Syrian President Bashar al-Assad's government throughout the nearly seven-year war that has killed hundreds of thousands of people and driven millions from their homes since it began with a crackdown on pro-democracy protests.
Russia helped turn the tide of the war in Assad's favor by launching a campaign of air strikes in September 2015 and stepping up its involvement on the ground.
Putin declared victory during a visit to Russia's air base in Syria on December 11, saying that Russian and Syrian forces had "crushed the most combat-capable international terrorist group" and announcing a partial withdrawal of Russian troops.
Western officials say that the Russian campaign, particularly in its earlier stages, has focused heavily on targeting rebels seeking Assad's ouster rather than IS militants.
Addressing the military personnel on December 28, Putin said that "more than 48,000" Russian military officers and personnel "took part in the operation in Syria."
Media reports have said that figure, which Defense Minister Sergei Shoigu mentioned earlier in December, includes support staff.
Putin said that two Russian bases in Syria -- the Hmeimim air base and a naval facility at the Mediterranean port of Tartus -- will continue to operate "on a permanent basis."
"This is an important factor in the defense of our national interests, providing for Russia's security in one of the key strategic areas," he said.
With reporting by TASS, Interfax, and Meduza