The Canadian government has warned that Canadians in Russia who hold dual citizenship must leave the country as soon as possible or risk conscription for mandatory military service.

This warning comes as Russian President Vladimir Putin carries out a partial military mobilization that could see up to 300,000 citizens and reserve soldiers sent to fight in the Russian war in Ukraine.

The Canadian travel warning stated that "dual citizenship is not legally recognized in Russia," adding that Russian authorities may choose to consider anyone holding dual citizenship as a Russian citizen and deny them access to Canadian consular services.

For Canadians still in Russia, leaving may be more difficult than ever since Russia launched a full-scale invasion of Ukraine on February 24.

Since Putin announced the partial military mobilization on September 21, flight availability, which was already limited, has become even scarcer.

Many flights are fully booked weeks in advance. Ottawa warns that any Canadian still in Russia should leave while commercial flights are still available.

"You should not rely on the Government of Canada to help you leave the country," the federal travel guidelines said.

After suffering heavy losses on the battlefield amid the recent Ukrainian counteroffensive in the Kharkiv region, the Kremlin has struggled to replenish its forces there.

The Associated Press reported that it even resorted to recruiting inmates. On Friday, Putin escalated the war further by signing treaties to annex four partially illegally occupied Ukrainian regions, to which Ukrainian President Volodymyr Zelensky responded by submitting a fast application to join NATO.