A member of Russian President Vladimir Putin's powerful Security Council on Tuesday warned that the more destructive the weapons that the West supplied to Ukraine, the higher the risk of "nuclear apocalypse".
Russia, which has more nuclear weapons than any other state, has repeatedly said the West is engaged in a proxy war with Russia over Ukraine that could escalate into a much bigger conflict.
The United States has committed $37 billion in security assistance to Ukraine since Putin sent troops into Ukraine in February last year.
US President Joe Biden told fellow G7 leaders on Friday that he backed a joint effort with allies to train Ukrainian pilots on F-16 fighter jets, according to a senior US Administration official, though there is no commitment as yet to supply the jets themselves.
"The more weapons are supplied, the more dangerous the world will be," former Russian president Dmitry Medvedev, now deputy chairman of the Security Council, told the Russian state news agencies TASS and RIA while on a trip to Vietnam and Laos.
"And the more destructive these weapons are, the more likely the scenario becomes of what is commonly called a nuclear apocalypse," Medvedev was quoted as saying.
The West says it wants to help Ukraine defeat Russia but has repeatedly insisted it does not want to trigger a direct confrontation between the US-backed NATO military alliance and Russia.
But Medvedev said NATO did not appear to be taking the possibility of nuclear conflict seriously.
"They are wrong. And at some point, events can move in a completely unpredictable scenario. And the responsibility will lie entirely with the North Atlantic Alliance," RIA quoted him as saying.
The Russian military said on Tuesday it had routed militants who had penetrated the Belgorod region from Ukraine, killing more than 70 "Ukrainian nationalists".
Medvedev said the attackers were "scumbags" who should be exterminated "like rats".
"Responsibility ... is carried by the Kyiv regime, and ultimately by its sponsors overseas - that is, Washington and the countries of the European Union, along with affiliated states like Britain and others," Medvedev said, according to TASS.
"This is their responsibility, direct and immediate."
