Russian President Vladimir Putin has called an explosion that injured more than a dozen people in St Petersburg earlier this week an act of "terror".
The bombing, which struck a local supermarket on Wednesday night, did not kill anyone but injured 14 people, six of whom remain in hospital, according to Russian state officials.
"As you know, an act of terror took place in St Petersburg yesterday," Putin said on Thursday.
Speaking at an awards ceremony for military officers that have taken part in Russia's intervention in Syria, Putin said security forces should "act decisively", but within the confines of Russian law, in their search for the suspects.
If law enforcement feels threatened, they should "liquidate [the] bandits on the spot", he said.
Though Putin described the bombing as an act of "terror", local authorities initially opened an investigation into "attempted murder of two or more people".
The probe has since been taken over by Russia's National Anti-Terror Committee.
Dmitry Peskov, Putin's press secretary, echoed Putin's "terror" designation on Thursday but said the Kremlin did not consider the security agencies' initial investigation to be "inadequate".
"As some details [of the investigation] are revealed, they are analysed and are reported to the president. On the basis of this reports, the president makes his conclusion," Peskov said.
Seven suspects linked to the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group have been arrested in connection with the bombing, according to Russia's Federal Security Service.
The suspects planned to bomb a popular cathedral in St Petersburg, as well as other crowded sites, Russian officials said.
Earlier this month, Putin thanked US President Donald Trump for a tip delivered by the CIA that helped Russian authorities stop a series of bombings that were reportedly planned in St Petersburg.