Russia has ordered four men accused of killing at least 137 people in an attack at a Moscow concert hall to be held in custody on "terror" charges, with the death toll expected to climb as more than 100 people remain hospitalized.The men face life in prison, although Russian officials have clamored for the lifting of a moratorium on the death penalty to deliver even harsher sentences.In a series of late-night court hearings in Moscow that ran into the early hours of Monday, the four men, with bruises and cuts over their faces, were dragged into the court in front of dozens of reporters who had assembled at the capital's Basmanny district court.Russian Federal Security Service (FSB) officers wheeled one of the men into the hearing on a medical gurney, following reports and videos on Russian social media of violent interrogations after the men were arrested on Saturday.The court said two of the defendants had pleaded guilty.The Friday evening attack has been claimed by Islamic State, though Russian officials have not commented on their possible involvement.In his only public remarks since, President Vladimir Putin pointed to a Ukrainian connection, saying the four suspects gunmen were arrested while trying to flee there. Kyiv has strongly denied any links.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.Russian investigators have yet to issue a statement on the other seven suspects said to have been arrested in connection with the attack.The four suspected shooters were all citizens of the Central Asian republic of Tajikistan, Russian state media reported.The Islamic State (IS) 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.