Four men accused of carrying out Friday's attack on a Moscow concert hall that left 137 people dead were remanded in custody on Sunday, as Russia observed a national day of mourning following the mass killing 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 was 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 links.
Putin has made no public reference to the Islamic State (IS) group's claims of responsibility for the attack.
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 and then set fire to the building.
It is the deadliest attack in Europe to have been claimed by IS.
Russia's Investigative Committee, which probes major crimes, posted a video of the four suspects being dragged into its headquarters in Moscow.
There was no statement on the other seven suspects said to have been arrested in connection with the attack.
Officials have said the gunmen were all foreign nationals.
'Machine guns, knives, firebombs'
The Islamic State group on Saturday said the concert hall attack was "carried out by four IS fighters armed with machine guns, a pistol, knives and firebombs" as part of "the raging war" with "countries fighting Islam."
A video lasting less than two minutes, apparently filmed by the gunmen, was posted on social media accounts typically used by IS, according to the SITE intelligence group.
The video, which appears to have been filmed from the lobby of the concert venue, shows several individuals with blurred faces and distorted voices firing assault rifles with motionless bodies strewn on the floor. A fire could be seen in the background.
Russian investigators said that after walking through the theater and shooting spectators, the gunmen set fire to the building, trapping many inside.
Health officials said the number of wounded had risen to 182, with 101 people still being treated at the hospital, of whom 40 were in "critical" or "extremely critical" condition.
The attack was the deadliest in Russia since the Beslan school siege in 2004.
Russia's Emergency Situations Ministry has so far named 29 of the victims, but the blaze has complicated the process of identification.
The ministry on Sunday posted a video of heavy equipment arriving at the burned-down concert hall to dismantle damaged structures and clear debris.
