Moscow's Basmanny district court on Monday ordered the pre-trial detention for two months of all four suspects in Friday's deadly concert hall attack.

Russian President Vladimir Putin has promised to punish those behind the attack at the Crocus City Hall, in which the death toll has now risen to at least 137.

What happened in the courtroom?

The four main suspects between the ages of 19 and 32, and identified in Russian media as Tajik nationals, were charged with committing a deadly group terrorist attack. They face a maximum sentence of life imprisonment. 

The suspects began to appear in court shortly before 11 p.m. local time on Sunday with bruises visible on their faces. One of the men, in a wheelchair and wearing a hospital gown, was reportedly brought from intensive care.

All four appeared separately, being led into a cage in the courtroom by Federal Security Service officers. Two of the defendants pleaded guilty, the court said.

The four, allegedly the gunmen in Friday's attack, are among 11 people arrested by police in connection with the incident. They were reportedly detained in the Bryansk region, about 340 kilometers (210 miles) southwest of Moscow.

Putin says Islamists behind attacks but still insists on Ukraine narrative 

Speaking at a meeting of government officials on Monday, Putin acknowledged that "radical Islamists" had been behind the attack but repeated his accusation that Ukraine could have played role — despite strong denials from Kyiv.

The president said investigators were yet to determine who ordered the attack but added that it was necessary to find out "why the terrorists, after committing their crime, tried to flee to Ukraine, and who was waiting for them there."

Putin claimed Ukraine had been using cross-border attacks to deflect attention from its battlefield setbacks, adding, "bloody intimidation acts like the Moscow terror attack look like a logical part of this pattern."

Putin also said investigators still needed to clarify several questions, including why the attackers struck during the Muslim holy month of Ramadan given their claims to religious piety.

What we know about the attack

Sunday had been declared a day of national mourning with events canceled and flags lowered to half-staff.

The attack on the concert hall was the deadliest such incident in Russia in the last two decades. Camouflage-clad gunmen burst into the venue and sprayed people with bullets just before Soviet-era rock group Picnic was set to perform its hit "Afraid of Nothing."

The so-called "Islamic State" offshoot "Islamic State Khorasan Province" (ISKP), which is based in Afghanistan and Pakistan, has claimed responsibility for the attack. The militant group has since released footage of the incident and US officials have said they believe the claim.

The Kremlin on Monday said it would not comment on the ISIS-K claims of responsibility.

"The investigation is ongoing. No coherent version has been voiced yet. We are talking only about preliminary data," Kremlin spokesman Dmitry Peskov told reporters. 

Peskov added that President Vladimir Putin had no plans to visit the site of the attack.

French President Emmanuel Macron on Monday said France had information that an offshoot of IS had carried out Friday's attack. 

"It was an entity of Islamic State that planned the attack and carried it out," Macron told reporters, adding that "this particular group made several attempts [at attacks] on our own soil."

Macron warned Russia against any "exploitation" of the attack. The French leader said it would be "cynical and counterproductive for Russia to use this context to try and turn it against Ukraine." The French government raised its terror alert warning to its highest level on Sunday, in light of the shootings in Moscow.

Putin has not publicly mentioned the Islamist group's involvement but said the attackers were trying to escape to Ukraine. Kyiv has strongly denied any connection.

rc/wmr (dpa, Reuters)