MOSCOW — Russia on Monday cast doubt on assertions by the United States that the Islamic State militant group was responsible for a gun attack on a concert hall outside Moscow which killed 137 people and injured 182 more.

In the deadliest attack inside Russia for two decades, four men burst into the Crocus City Hall on Friday night, spraying people with bullets just before the rock group Picnic was to perform its hit Afraid of Nothing.

Four men, at least one a Tajik, were remanded in custody for terrorism. They appeared separately, led into a cage at Moscow's Basmanny District Court by Federal Security Service officers, Reuters reported.

The Islamic State has claimed responsibility for the attack, a claim which the United States has publicly said it believed, and the militant group has since released what it says is footage from the attack. US officials said they warned Russia of intelligence about an imminent attack earlier this month.

Russian President Vladimir Putin has not publicly mentioned the Islamist militant group in connection with the attackers, who he said had been trying to escape to Ukraine.

Ukraine has denied any role in the attack.

Russia's Foreign Ministry spokeswoman Maria Zakharova called into question US assertions that the Islamic State, which once sought control over swathes of Iraq and Syria, was behind the attack.

"Attention — a question to the White House: Are you sure it's ISIS? Might you think again about that?" Zakharova said in an article for the Komsomolskaya Pravda newspaper.

Zakharova said the US was spreading a version of the "bogeyman" of Islamic State to cover its "wards" in Kyiv and reminded readers that Washington supported the "mujahideen" fighters who fought Soviet forces in the 1980s.

The US has intelligence confirming Islamic State's claim of responsibility two US officials said on Friday.

French President Emmanuel Macron on Monday said France has information that the Islamic State carried out Friday's attack in a Moscow concert hall, warning Russia against exploiting the attack by blaming it on Ukraine.

France has intelligence that "it was an entity of Islamic State that planned the attack and carried it out," Macron told reporters after arriving on a trip to the French South American region of French Guiana.

He added that "this particular group made several attempts (at attacks) on our own soil".

France raises alert level

The French government said late on Sunday it was raising its terror alert warning to its highest level following the attack in Moscow.

Near the Crocus City Hall in suburban Moscow, a somber sea of Russian citizens of all ages converged to pay their respects to the victims of Friday's terrorist attack.

In central Moscow, landmarks such as the Kremlin and the State Duma building flew their flags at half-mast on Sunday.

International cooperation is necessary in the fight against terrorism, but the dialogue is currently paused due to escalated global tensions, Kremlin spokesperson Dmitry Peskov said on Monday.

"The fight against terrorism is a constant process that requires full-scale international cooperation, but now, due to the period of very tense confrontation, this cooperation is not being carried out in full, it is not carried out at all," the spokesperson said.

Peskov added that Russia's special services are working independently on the terrorist attack at the concert venue and the country currently has "no contacts with the West" regarding the investigation into the attack.

AGENCIES—XINHUA