Russian President Vladimir Putin said Monday the gunmen who carried out the concert hall attack that killed over 130 people in a Moscow suburb last week were “radical Islamists.”

Speaking in a meeting with government officials, Putin said the killings were carried out by extremists “whose ideology the Islamic world has been fighting for centuries”.

Putin, who said over the weekend the four attackers were arrested while trying to escape to Ukraine, didn’t mention the affiliate of the Islamic State group that claimed responsibility for the attack. He again refrained from mentioning IS in his remarks Monday.

He also stopped short of saying who ordered the attack but said 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.”

After the IS affiliate claimed responsibility, US intelligence backed up their claims. French President Emmanuel Macron said France has intelligence pointing to “an IS entity” as responsible for the Moscow attack.

Earlier Monday, Kremlin spokesman Dmitry Peskov refused to assign blame, urging reporters to wait for the results of the investigation in Russia. He also refused to comment on reports that the US warned authorities in Moscow on March 7 about a possible terrorist attack, saying any such intelligence is confidential.