Ukrainian President Volodymyr Zelenskyy has again dismissed a view expressed by Russian President Vladimir Putin that Ukraine may have played a role in last Friday's deadly attack on a concert hall near Moscow.

Putin said on Monday that the attack was carried out by radical Islamists, but added that the atrocity may be linked to a series of attempts by "those who have been at war with our country since 2014 by the hands of the neo-Nazi Kyiv regime," referring to Ukraine.

On the same day, Zelenskyy said Putin accused Ukraine again. He called Putin "a sick and cynical creature" and said, "everyone is a terrorist to him, except for himself."

Gunmen stormed the concert hall on Friday night, killing at least 139 and injuring 182 others. Four suspected attackers have been indicted.

The Amaq news agency, which is linked to the Islamic State group, has said the group claims responsibility for the attack. The United States and France have also echoed the view and dismissed any Ukrainian involvement.

Observers say Putin aims to step up his offensive in Ukraine and keep in check dissidents inside Russia by claiming that Ukraine may have been involved in the attack.