China said Thursday it has formally arrested two Canadians who have been detained for months on national security grounds, in a case that has inflamed tensions between Ottawa and Beijing.
Ottawa denounced the move and demanded the pair's prompt release.
Former diplomat Michael Kovrig is "suspected of collecting state secrets and intelligence," while businessman Michael Spavor is suspected of "stealing and illegally offering state secrets" abroad, Chinese foreign ministry spokesman Lu Kang said at a regular briefing.
Lu said the two were arrested "recently", but did not provide a date, and added that he had no information about where they were being held.
At a news conference in Paris, Canadian Prime Minister Justin Trudeau called the arrests "unacceptable" and vowed to "stand up" for Kovrig and Spavor, saying they have been "arbitrarily detained."
Canada's foreign ministry, meanwhile, said it "strongly condemns" the arrests, and reiterated its demand "that China immediately release Mr Kovrig and Mr Spavor."
Though no link has been officially made, the detention of the two is thought to be in retaliation for Canada's December 1 detention on a US extradition request of Meng Wanzhou, a top executive with 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.
Days after Meng's extradition was announced, China said it suspected Kovrig, who works for the International Crisis Group think tank, of spying and stealing state secrets, and alleged that Spavor -- who organised trips to North Korea -- had provided him with intelligence.
Spying charges could expose them to tough prison sentences.
- 'Unacceptable' conditions -
No details of the men's detention or health conditions were provided due to Canadian privacy laws, but officials said they would press for further access to both detainees.
Foreign ministry spokesman Lu said "Chinese judicial authorities are handling the cases according to law", and that Spavor and Kovrig's "legitimate rights and interests are fully guaranteed".
A group of Canadian parliamentarians had earlier complained to Chinese officials that the two have been denied access to lawyers, and remain in "completely unacceptable" detention conditions.
Meng is allowed to live in her Vancouver mansion, although her mobility is limited. She made her latest court appearance last week as she fights extradition to the United States -- a process that could take months or even years.
She has been ordered to wear an electronic monitoring device and hand over her passports after being released on bail in mid-December on a Can$10 million (US$7.4 million) bond.
She recently wrote in open letter to supporters that "despite restrictions on my permitted range of movement, the colour and scope of my heart have never been so rich and broad."
Two other Canadians convicted of drug trafficking, meanwhile, have been sentenced to death. Canada has called the death penalties for Fen Wei and Robert Lloyd Schellenberg "cruel and inhumane" asked for clemency on their behalf.
Beijing also recently blocked Canadian shipments of canola and pork worth billions of dollars.
Ottawa has rallied the support of a dozen countries, including Britain, France, Germany and the US, as well as the EU, NATO and the G7, in its diplomatic feud with China.
Washington meanwhile stepped up its battle against Huawei on Wednesday, effectively barring the company from the US market and restricting US sales to the firm.
The United States has also urged allies to shun Huawei's 5G technology, warning that it could serve the interests of Chinese intelligence services.
Canada's Public Safety Minister Ralph Goodale has said a 5G decision would be announced in the coming months.