Vladimir Putin has acknowledged for the first time that radical Islamists carried out the worst terrorist attack in Russia in two decades but repeated his unproven claim that Ukraine was also involved.

It comes as the Kremlin faces calls to bring back the death penalty with videos emerging of Russian security officers torturing suspected attackers who were detained over the weekend, including cutting off one man’s ear and force-feeding it to him.

Speaking at a televised video conference with senior officials on Monday evening, Putin suggested the murderous attack was “just a link in a whole series of attempts by those who have been at war with our country since 2014 by the hands of the neo-Nazi Kyiv regime”, he said.

“Of course, it is necessary to answer the question, why, after committing the crime, did the terrorists try to go to Ukraine? Who was waiting for them there?” he added.

The Islamic State terrorist group has claimed responsibility for the Friday night attack that killed at least 139 people.

The United States has said it has intelligence that confirms that claim and that the group appears to have acted alone.

Ukraine has vehemently denied any involvement in the attack.