Although no link has been officially made, the detentions are thought to be in retaliation for Canada's detention on December 1 a year ago of Huawei Technologies Co (華為) chief financial officer Meng Wanzhou (孟晚舟), who is accused of breaching sanctions on Iran. She made her latest court appearance last week as she fights extradition - a process that could take months or even years.
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.
"We hope that Canada will not make irresponsible remarks about China's own law enforcement and judicial proceedings".
"Canada strongly condemns their arbitrary arrest as we condemned their arbitrary detention on December 10", Global Affairs spokeswoman Brittany Fletcher said in a statement.
Goodale said the arrests are an "arbitrary action" and that Canada will continue to demand the two be treated fairly.
No details of the men's detention or health conditions were provided due to Canadian privacy laws, but officials said that they would press for further access to the detainees.
When asked if he'd call Chinese President Xi Jinping personally to protest the arrests, Trudeau said Canada is focused on "things that are going to help the Canadians being detained".
China's arrests of two Canadians are alarming foreign partners much more deeply than leaders in Beijing realize, says one of Canada's former ambassadors to the People's Republic.
"When Chinese businesses are wrongfully treated, China has the right to take measures to safeguard our legitimate and lawful rights and interests", he said. China has also never announced where the men are being held. After 158 days of arbitrary detention, Michael still hasn't been allowed to see his family or a lawyer. Having been formally arrested, the two are likely to face trial soon.
While Canada says China has made no specific link between the detentions of the two men and Meng's arrest, experts and former diplomats say they have no doubt it is using their cases to pressure Canada.
Meng, 47, is the daughter of Huawei Technologies Co Ltd's billionaire founder, Ren Zhengfei.
Meng, who is now on bail, faces charges of fraud related to an alleged breach of USA sanctions on Iran.
She was ordered to wear an electronic anklet and hand over her passports after being released on bail in mid-December on a C$10 million (S$10.2 million) bond.
Meng - who is now fighting extradition to the United States - is allowed to live in her Vancouver mansion, although her mobility is limited.
Citing Huawei's threat to USA national security, the Commerce Department had announced hours earlier on Wednesday that it named Huawei to the so-called "Entity List".