Russian President Vladimir Putin's "invasion of Crimea, his interference in the Donbass, his actions elsewhere around the world... most notably on UK soil, in Salisbury, are things that require a clear and firm response," Trudeau told reporters in the Latvian capital Riga.

A key NATO summit opens in Brussels on Wednesday, with the agenda including US President Donald Trump's demands for extra spending from allies along with the growing threat members see from Russia on its eastern flank.

Britain on Monday accused Russia of causing the death of a homeless British woman from exposure to the nerve agent Novichok.

The fatality follows the poisoning of a former Russian double agent Sergei Skripal and his daughter in Salisbury in March. They have since recovered.

"We certainly hope that Russia will choose to become a more positive actor in the global sphere than it has chosen to be in the past years," Trudeau added.

The Kremlin, meanwhile, on Tuesday branded NATO a relic of the Cold War.

Trudeau also said that Canada would extend its leadership of the NATO battalion based in Latvia until 2023 and boost the number of its troops deployed there from 455 to 540.

- 'Perfect gift' -

Canada leads one of four battalions deployed by the Western defence alliance on its eastern flank in 2017 in a deterrence and defence posture following Russia's annexation of Crimea in 2014.

"We are ready to support our allies while facing global threats to security," said Trudeau, adding that Canada's current mission initially slated to expire in 2019, "will be prolonged for four years."

"Canada will not change its attitude towards security of the Baltic countries," Trudeau told reporters at a press conference with his Latvian counterpart Maris Kucinskis.

The Latvian premier hailed Ottawa's decision to extend its mission as "the perfect gift to Latvia on its centenary".

Later on Tuesday, Trudeau visited the Canadian troops deployed for Operation Reassurance, which is Canada's largest sustained military presence in Europe in more than a decade.

In total, over 1,000 NATO troops from nine alliance members are deployed in the Latvian battalion.

The other three NATO battalions are based in Estonia, Lithuania and Poland and are led by Britain, Germany and the United States, respectively.

Trudeau's visit is the first ever by a Canadian head of government to Latvia, his office said.

He now heads to Brussels for the NATO summit on July 11 and 12.