Putin vows quick, tough response

MOSCOW — Russian President Vladimir Putin pledged to track down and punish those behind the deadly attack on a concert hall, expressing condolences to families.

"I express my deep, sincere condolences to all those who lost their loved ones," Putin said in an address to the nation on Saturday. "The whole country and our entire people are grieving with you.

"Terrorists, murderers, non-humans … have only one unenviable fate: retribution and oblivion," Putin said.

Russian television showed security services interrogating four men on a road in the western Bryansk region, which borders both Ukraine and Belarus.

"They tried to escape and were traveling toward Ukraine, where, according to preliminary data, a window was prepared for them on the Ukrainian side to cross the state border," said Putin.

Ukrainian President Volodymyr Zelensky, in his evening address on Saturday, dismissed the suggestion that Kyiv had been involved. He said Russia was trying to shift blame.

Russia has arrested 11 people in connection with the attack, the FSB security service said. Earlier, the agency had said the attackers had "contacts" in Ukraine, without elaborating.

"All the perpetrators, organizers and those who ordered this crime will be justly and inevitably punished. Whoever they are, whoever is guiding them," Putin said.

"We will identify and punish everyone who stands behind the terrorists, who prepared this atrocity, this strike against Russia, against our people."

A senior Russian lawmaker, Andrey Kartapolov, said that if Ukraine was involved, then Russia must deliver a "worthy, clear and concrete" reply on the battlefield.

The US embassy in Moscow issued a security alert to US citizens on March 7 saying it was monitoring reports that extremists had "imminent plans to target large gatherings" in Moscow, including concerts.

The warning advised US citizens to avoid large gatherings for the coming 48 hours.

Agencies via Xinhua