Vyacheslav Volodin, speaker of the lower house of parliament and a member of Putin's Security Council, was responding to a vote in the European Parliament urging EU countries to give such approval to Kyiv.
"What the European Parliament is calling for leads to a world war using nuclear weapons," Volodin wrote on Telegram.
His message was entitled "For those who didn't get it the first time" - an apparent reference to a warning by Putin last week that the West would be directly fighting Russia if it let Ukraine fire the long-range missiles onto Russian territory.