OTTAWA, Canada -- Canadian Prime Minister Justin Trudeau announced Monday a ban on Russian oil imports, saying oil revenues have helped to prop up President Vladimir Putin and Russian oligarchs and wage war against Ukraine.

He said Ottawa would also be supplying Ukraine with anti-tank weapons and ammunition, in addition to three previous arms shipments.

"Today, we are announcing a ban on all imports of crude oil from Russia, an industry that has benefited President Putin and his oligarchs greatly," Trudeau told a news conference.

"And while Canada has imported very little amounts in recent years, this measure sends a powerful message," he added.

Canada, with the fourth largest reserve in the world, is a net oil exporter, but still imports significant amounts from countries including the United States and Saudi Arabia, and until recently Russia too, for domestic consumption.

According to government and industry data, Canadian oil imports from Russia fell from more than 17,000 barrels in 2019 to nearly zero the following year.

Trudeau noted that the Russian oil sales account for about one-third of Moscow's government revenues.

"Our message is clear," Trudeau said. "This unnecessary war must stop now. The costs will only grow steeper. And those responsible will be held accountable."

"We have seen over the past couple of days that Putin made a grave miscalculation. He thought it would be easy to conquer Ukraine... He thought the West would be divided and uncertain in its response," he said. "He was terribly wrong on both counts."

Defense Minister Anita Anand said 100 shoulder-mounted Carl Gustaf anti-tank weapons and 2,000 rockets would be delivered to Ukraine "as quickly as possible in the coming days."

Putin laid down his conditions on Monday for stopping the invasion of Ukraine, as sanctions continue to rain down on Russia and Westerners warned that more could still be imposed.