YEREVAN, MARCH 25, ARMENPRESS. Moscow's Basmanny district court on Sunday charged four suspects with acts of terrorism in connection with the attack in Crocus Citi Hall on March 22, according to Moscow courts' official Telegram channel.

It said the men, identified by Russian media as all being citizens of the Republic of Tajikistan living in Russia, would be remanded in pre-trial custody until May 22. Two of the four have pleaded guilty to all charges.

According to Russian authorities, 11 people have been detained, including the four suspected gunmen, who fled the concert hall and made their way to the Bryansk region, about 340 km southwest of Moscow.

Russian president Vladimir Putin declared Sunday a national day of mourning after pledging to punish all those behind the attack, in which 137 people were killed, including three children, and 182 were injured. Islamic State has claimed responsibility for the attack.

Friday's attack was the deadliest on Russian territory since the 2004 Beslan school siege, when Islamist militants took more than 1,100 people hostage. 333 people died at the time, more than half of them children.