Spavor, a businessman based near the China-North Korea border, and Kovrig, a former Canadian diplomat and geopolitics researcher, were first detained by Chinese state security on December 10, a week after Canadian airport authorities detained senior Huawei executive Meng Wanzhou at the behest of US law enforcement.
China's Foreign Ministry said Kovrig was arrested on charges of gathering state secrets, and Spavor on charges of stealing secrets for overseas forces.
A news portal run by China's Central Political and Legal Affairs Commission previously accused Mr Kovrig - on leave from Canada's foreign service - of spying and stealing state secrets while employed by the International Crisis Group, and said Mr Spavor was his primary contact and supplied him with intelligence.
"Everything in China is done in accordance with law", Lu, the Chinese government spokesman, told reporters Thursday.
A pair of Canadians, who have been detained in China since a year ago, have been formally arrested and charged. According to the Canadian government, Chinese law allows for people to be held for 13-and-a-half months after an official arrest before charges are filed.
"We reiterate our demand that China immediately release Mr Kovrig and Mr Spavor". "The actions we have taken are entirely law-based".
"Michael has been unjustly detained and has now been unjustly arrested", the group said in a written statement.
Kovrig, a former diplomat, and Spavor, an entrepreneur who frequently led tours to North Korea, were both detained by Chinese officials in December a year ago. The two have been allowed short consular visits once a month, during which they are not allowed to discuss the cases against them with Canadian diplomats.
Ms Wanzhou is now fighting her extradition to the USA in Canada's courts. Kovrig also holds Hungarian citizenship.
Meng, 47, is the daughter of Huawei Technologies Co Ltd's billionaire founder, Ren Zhengfei.
Meng Wanzhou, seen here as she leaves her home in Vancouver last week, was arrested in Canada at the request of the U.S. This move will ban US companies from selling or transferring USA technology to Huawei without US government approval.
She was arrested at Vancouver's airport in December on a U.S. warrant and is fighting extradition on charges that she conspired to defraud global banks about Huawei's relationship with a company operating in Iran.
The U.S. has pressured other countries to limit their use of Huawei's technology, warning they could be opening themselves up to surveillance and theft of information.
Meng was released from jail in December on C$10 million ($7.5 million) bail and must wear an electronic ankle bracelet and pay for security guards.
Both Canadians have a long history of working in China.