Michael Kovrig, a former diplomat, and Michael Spavor, a businessman, were detained in December after Meng Wanzhou was arrested in Canada on suspicion of fraud and breaching sanctions on Iran.
Ms Meng is suing Canada over her arrest, which was made at the request of the US.
China has condemned Ms Meng’s arrest.
The diplomatic spat has hurt Canada-China relations, and the arrest of the two Canadians had been seen as Beijing’s retaliation for its detention of Ms Meng.
Canada officially launched her extradition process on Friday but the legal process can be lengthy and remains in its early stages.
Speaking to journalists on Monday, Prime Minister Justin Trudeau said his government was “very concerned with this position that China has taken” on the two detained men.
“It is unfortunate that China continues to move forward on these arbitrary detentions, and we will continue to stand up for these Canadians,” he said.
Mr Trudeau has previously called for the release of both men.
What are China’s allegations against the pair?
They were set out for the first time on Monday.
Mr Kovrig, who now works for Brussels-based think tank the International Crisis Group (ICG), “is suspected of spying and stealing national secrets for foreign agents”, Chinese state media reported, citing authorities.
It said that Mr Spavor “had provided intelligence to Mr Kovrig and was an important intelligence contact of [his]”.
Mr Kovrig had entered China frequently since 2017 with “a regular passport and a business visa”, the authorities said.
Until now China had not provided detailed allegations against the pair, only saying that they were suspected of hurting China’s security.
The ICG told the BBC that the group was aware of Monday’s reports but had “heard nothing official about any charges being laid against our colleague, Michael Kovrig”.
“Michael’s work for Crisis Group has been entirely transparent and in the open as all who follow his work can attest. Vague and unsubstantiated accusations against him are unwarranted and unfair,” a spokesperson said.
The think tank has previously said his work involved meeting officials, academics and analysts and attending conferences.
Mr Spavor lives in the Chinese city of Dandong, which borders North Korea. He has close ties to the North Korean regime and brings foreign investors there on tours.
Where are we in the Meng extradition process?
Ms Meng, 47, will next appear in court on Wednesday, when it will be confirmed that Canada has issued a legal writ over her extradition to the US. A date for an extradition hearing will be set.
But this is still the early stages. A judge must authorise her committal for extradition and the justice minister would then decide whether to surrender her to the US.
There will be chances for appeal and some cases have dragged on for years.
Why is Ms Meng suing Canada?
Ms Meng’s lawsuit – filed in British Columbia’s Supreme Court on Friday – seeks damages against the Royal Canadian Mounted Police (RCMP), Canadian Border Services Agency (CBSA) and the federal government for allegedly breaching her civil rights under Canada’s Charter of Rights and Freedoms.
Her detention was “unlawful” and “arbitrary”, the suit says, and officers “intentionally failed to advise her of the true reasons for her detention, her right to counsel, and her right to silence”.