A close ally of President Vladimir Putin said on Sunday that deliveries of offensive weapons to Kyiv that threaten Russia's territories will lead to a global catastrophe and make arguments against using weapons of mass destruction untenable.

Vyacheslav Volodin, speaker of the Duma - Russia's lower house of parliament - warned that the United States and NATO's support of Ukraine is leading the world to a "terrible war".

"If Washington and NATO countries supply weapons that will be used to strike civilian cities and attempt to seize our territories, as they threaten, this will lead to retaliatory measures using more powerful weapons," Volodin said on the Telegram messaging app.