Canadian Prime Minister Justin Trudeau announced new military aid for Ukraine during an unannounced trip to war-time Kyiv on Saturday, as Ukraine braces for a counteroffensive against Russian forces and grapples with regular air strikes.

Trudeau paid his respects at a memorial site in central Kyiv to Ukrainian soldiers who have been killed fighting pro-Russian forces since 2014, and also met President Volodymyr Zelenskiy for talks.

"We will be there with (you) as much as it takes, for as long as it takes," he said, sitting across from the Ukrainian leader in footage of the talks released by Kyiv authorities.

NATO member Canada, which has one of the world's largest Ukrainian diasporas, has supplied military and financial assistance to Kyiv during the full-scale invasion launched by Russia in February 2022.

"Today, I can announce that we will provide 500 million dollars in new funding for military assistance," he told reporters at a joint press conference.

Ukraine wants to join the NATO military alliance as fast as it can, but Zelenskiy has said he recognised that cannot happen while the war with Russia is raging.

"Canada supports Ukraine to become a NATO member as soon as conditions allow for it. Ukraine and Canada look forward to addressing these issues at the NATO Summit in Vilnius in July 2023," said a joint declaration adopted after the talks.

At the talks, Zelenskiy said Ukraine was grateful to Canadians for their support: "Thank you so much. The people of Canada, and of course, to all your team, to the government and parliament. Really. It's (such) necessary help," he said.

Trudeau's trip to Kyiv followed a night of Russian missile and drone attacks on targets outside the capital, including Odesa, Poltava region and Kharkiv.

The Canadian prime minister was accompanied by Deputy Prime Minister Chrystia Freeland, a Ukrainian speaker.