Russians mark day of mourning following deadly concert hall attack. Here's what to know

People line up at a makeshift memorial outside Crocus City Hall near Moscow on March 24. Maxim Shemetov/Reuters

Russian President Vladimir Putin declared Sunday a day of national mourning for the 137 victims in Friday's attack on a Moscow concert hall. Putin vowed to punish the perpetrators and expressed condolences to those who lost loved ones.

"The whole country, our whole people, mourns with you," he said. The attack is Russia's deadliest in two decades.

The deadly attack came barely a week after Putin secured his fifth presidential term. A large-scale terror attack is damaging for a leader who portrays himself as someone able to guarantee order.

Catch-up on the latest developments:

• Authorities work to identify victims: Procedures to identify those killed in the terrorist attack at Crocus City Hall have begun, the city’s Department of Health said, according to Russian state news agency RIA Novosti. In a statement released online, the Russian Investigative Committee said 62 bodies have been identified so far, adding that "for the remaining victims, genetic examinations are being carried out to establish their identities." The investigation of the crime scene is ongoing, the statement said.
• Fighting terror in Syria and Turkey: Putin held separate calls with his Turkish and Syrian counterparts, Recep Tayyip Erdoğan and Bashar al-Assad, on Saturday and promised closer cooperation in fighting terrorism following the deadly concert attack, according to a Kremlin readout.
• UK accuses Russia of propaganda: UK Chancellor of the Exchequer Jeremy Hunt told British broadcaster Sky News that the UK government has “very little confidence in anything the Russian government says” with regards to the Kremlin’s claim that Ukraine was somehow involved in the Moscow Crocus City attack. On Saturday, Putin said in an address that the four attackers tried to escape to Ukraine.
• Russian Embassy says no warnings from US: The Russian Embassy in Washington says it did not receive any warnings about a potential terror attack in Moscow from the US, Ambassador to the US Anatoly Antonov told Russian state news agency RIA Novosti Sunday.