MOSCOW - Four men accused of involvement in a massacre at a Moscow concert hall that killed 137 people were remanded in custody Sunday, as Russia observed a national day of mourning following the attack claimed by the Islamic State.
All four suspects have been charged with terrorism, according to Moscow's Basmanny district court, and face life imprisonment. Their detention is set until May 22 but may be extended depending on the date of their trial.
The court said two of the defendants had pleaded guilty, and one of them, from Tajikistan, had "entirely acknowledged his guilt".
President Vladimir Putin has vowed to punish those behind the "barbaric terrorist attack", and on Saturday said the four gunmen had been arrested while trying to flee to Ukraine. Kyiv has strongly denied any connection to the attack.
READ: PUTIN VOWS RETRIBUTION FOR CONCERT HALL ATTACK, AS DEATH TOLL CLIMBS TO 133
Putin has made no public reference to the Islamic State (IS) group's claims of responsibility.
At least 137 people, including three children, were killed Friday evening when gunmen stormed the Crocus City Hall in Moscow's northern suburb of Krasnogorsk then set fire to the building.
It is the deadliest attack in Europe to have been claimed by IS.
Russia's Investigative Committee posted a video of the four suspects being dragged into its headquarters in Moscow.
There was no statement on the other seven suspects arrested in connection with the attack.
Officials have said the gunmen were all foreign nationals.