A close ally of President Vladimir Putin warned Western governments on Thursday that a nuclear war would ensue if they gave the green light for Ukraine to use long-range Western weapons to strike targets deep inside Russia.

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.

The Ukraine war has triggered the biggest confrontation between Russia and the West since the 1962 Cuban Missile Crisis, which is considered to be the time when the two Cold War superpowers came closest to an intentional nuclear war.

The outgoing head of NATO, Jens Stoltenberg, told The Times this week that the Kremlin leader had declared "many red lines" before but not escalated conflict with the West when they were crossed. Putin's spokesman said his comment was dangerous and provocative.

In a non-binding resolution adopted on Thursday, the European Parliament asked EU countries to "immediately lift restrictions on the use of Western weapons systems delivered to Ukraine against legitimate military targets on Russian territory."

Volodin wrote: "If something like this happens, Russia will give a tough response using more powerful weapons. No one should have any illusions about this." He said it appeared to Moscow that the West had forgotten the vast sacrifices made by the Soviet Union in World War Two.

He said Europeans should understand that it would take Russia's RS-28 Sarmat intercontinental ballistic missile, known in the West as Satan II, just 3 minutes and 20 seconds to strike Strasbourg, where the European Parliament meets.