China confirmed it has formally arrested two Canadians detained since December, in cases that have further strained tensions between the countries.

Michael Kovrig, who works for the International Crisis Group, and entrepreneur Michael Spavor “were arrested in accordance with the law,” Chinese Foreign Ministry spokesman Lu Kang told regular news briefing Thursday in Beijing. Kovrig was arrested on suspicion of spying on state secrets for foreign entities and other intelligence crimes, while Spavor was held on suspicion of stealing state secrets to foreign entities, Lu said.

The arrests took place “recently” with approval of Chinese prosecutors, Lu said, without elaborating. Canada’s Globe and Mail newspaper reported the arrests earlier Thursday and said the men had been moved from residential surveillance at an unknown location to an official detention center. Read more: Chinese Arrests Are All Too Familiar for Past Canadian Detainees

A news portal run by China’s Central Political and Legal Affairs Commission previously accused Kovrig -- on leave from Canada’s foreign service -- of spying and stealing state secrets while employed by the International Crisis Group. Spavor was his primary contact and supplied him with intelligence, the site said.

Heightened Tensions

The men were detained separately days after the arrest of Huawei Technologies Co. Chief Financial Officer Meng Wanzhou in Vancouver at the request of the U.S. They have since languished in China’s opaque legal system, allowed sporadic visits by Canadian authorities, but denied access to lawyers.

The confirmation of the arrests comes amid escalating tensions between China and the U.S. over Huawei. President Donald Trump this week moved to restrict Huawei’s ability to do business with U.S. companies. Ongoing trade talks between the two sides stalled last week, and Trump has moved to slap billions of dollars of new tariffs on Chinese goods.

Held in isolation, the two Canadians were questioned multiple times a day and unable to turn off the lights in their cells, Bloomberg reported in December. Canada sees the interrogation of Kovrig as violating the Vienna Convention -- to which China is a signatory -- that confers ongoing immunity for that period in his life.

“We must inform Canada that China is legally enforcing and arresting two Canadian citizens,” Lu said Thursday. “China has always acted in accordance with the law, and we hope that Canada will not make irresponsible remarks on China’s rule of law and judicial handling of cases.”