The Kremlin refused to comment Monday on the Islamic State group's claims that it was behind the deadliest attack in Russia in two decades, as rescuers searched for bodies amid the rubble of the burnt-out Moscow concert hall.
At least 137 people were killed when gunmen in camouflage stormed Crocus City Hall, shooting spectators before setting the building on fire in the most fatal attack in Europe to have been claimed by Islamic State jihadists.
The group has said several times since Friday that it carried out the attack, and IS-affiliated media channels have published videos of the gunmen inside the venue shooting concert-goers.
But in his only public remarks on the massacre, Russian President Vladimir Putin on Saturday pointed to a possible Ukraine connection, and no senior Russian official has commented on the IS claims.
"The investigation is still ongoing. No coherent version has yet been voiced," Kremlin spokesman Dmitry Peskov told reporters on Monday when asked why Russia had not addressed IS's claimed involvement.
"We are talking only about preliminary data. No version has been put forward yet," he added.
Officials expect the death toll to rise further, as rescuers were searching the site for remains on Monday and 97 are still in hospital.
Putin has no plans to visit the site of the attack, on the northwestern edge of Moscow, Peskov said.
He will hold a meeting with Russia's security chiefs, government officials and the heads of Moscow and the Moscow region later Monday.
The Kremlin also on Monday expressed confidence in the country's powerful security agencies, as questions swirl over how they failed to thwart the massacre despite public and private warnings by the United States' intelligence apparatus.
"Special services are working tirelessly, dealing with all the threats, all the challenges facing our country and society," Peskov said.
Putin, a former Soviet spy, headed the FSB briefly before becoming president and takes pride in its reputation as a team of feared intelligence operators.
A Moscow court has remanded four suspected gunmen in custody on "terror" charges, accusing them of being the assailants who stormed the concert hall and then set it on fire on Friday night.
They face life in prison, though some Russian officials have called for the lifting of a moratorium on the death penalty to deliver even harsher sentences.
The Kremlin said Monday that it was not involved in discussions about possibly bringing back capital punishment.
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 on their swollen faces -- were dragged in amid dozens of reporters who had assembled at the capital's Basmanny district court.
FSB officers wheeled one in to the hearing on a gurney, his eyes barely open.
Peskov refused to comment on reports and videos on social media that showed bloody interrogations of the suspects after they were arrested on Saturday.
The court identified them as Muhammadsobir Fayzov, Shamsidin Fariduni, Rachabalizoda Saidakrami and Dalerjon Mirzoyev. Russian state media said they were all citizens of Tajikistan.
Two of them pled guilty, the court said.
There has been no update on seven others Russia said it arrested in connection with the attack.
At least 137 people, including three children, were killed, according to the latest toll by Russian investigators.
After walking through the theatre shooting spectators, the gunmen set fire to the building, trapping many inside.
Victims died both of gunshot wounds and smoke inhalation, according to Russia's Investigative Committee.
More than 5,000 people were in the concert hall when the gunmen stormed in ahead of a sold-out rock concert, Russian state media cited a spokesperson from the venue owner as saying Monday.
Rescuers will continue sifting through the rubble and clearing debris at the site until Tuesday evening, said Andrey Vorobyov, governor of the Moscow region.
"The task is to remove the rubble to make sure there are no bodies underneath," Vorobyov said in a Telegram post.
Putin on Saturday vowed "retribution and oblivion" to the "terrorists, murderers and non-humans" who carried out the "barbaric terrorist act".
He said the four assailants had been arrested while trying to flee to Ukraine, where they had secured a "window" to cross the border.
The FSB has said the gunmen had "contacts" in Ukraine, without providing more details.
Ukrainian President Volodymyr Zelensky has denied any Ukrainian involvement.
On Monday, French President Emmanuel Macron warned Russia against "exploiting" the attack to blame Kyiv.
Russia observed a day of national mourning on Sunday, with dozens coming to lay flowers at a memorial to the victims, and tribute posters were erected on the sides of buildings and at transport stops across the country.
Russian schools were holding special lessons on "terrorism," on Monday, with children wearing white ribbons in honour of the victims, state TV presenters said in a news bulletin.
