A Canadian government source told The Globe and Mail that neither Michael Kovrig, a former diplomat, nor Michael Spavor, a China-based businessman who organised trips to North Korea, have been formally charged.

"Canada strongly condemns their arbitrary arrest as we condemned their arbitrary detention on Dec. 10," the Canadian foreign ministry said in a statement to the newspaper.

Though no link has been officially made, the detention of Spavor and Kovrig is thought to be in retaliation for Canada's December 1 detention on a US extradition request for Meng Wanzhou, a top executive of Chinese telecom giant Huawei who is accused of violating Iran sanctions.

The men were first accused of activities that "endanger China's security" -- a phrase often used by Beijing when alleging espionage.

China later announced it suspected Kovrig of spying and stealing state secrets and alleged that Spavor had provided him with intelligence.

Two other Canadians convicted of drug trafficking, meanwhile, have been sentenced to death. And Beijing recently blocked Canadian shipments of canola and pork worth billions of dollars.

Meng -- who is currently fighting extradition to the US -- is allowed to live in her Vancouver mansion, although her mobility is limited.

Meanwhile, a group of Canadian parliamentarians had earlier complained to Chinese officials that Kovrig and Spavor have been denied access to lawyers, and remain in "completely unacceptable" detention conditions.