China has accused two detained Canadians of spying, intensifying a diplomatic row between the two countries.

It came just days after Canada announced it will proceed with a request from the United States to extradite Meng Wanzhou, chief financial officer of the telecom giant Huawei.

Michael Kovrig, a former Canadian diplomat, was accused of spying and stealing state secrets and intelligence, with the help of Canadian businessman Michael Spavor.

It was the first time the two detained men's cases have been linked.

Mr Kovrig is a former diplomat who was working as an expert on Asia for the International Crisis Group think tank.

Mr Spavor is an entrepreneur known for contacts with high-ranking North Korean officials, including leader Kim Jong-un.

According to the official Xinhua news agency Mr Kovrig often entered China using an ordinary passport and business visas, and acquired information from Mr Spavor, who was his "main contact."

The two men were detained in December, days after Canada arrested Meng Wanzhou, who is also the daughter of Huawei's founder.

Three days ago Canada launched the extradition process against her, angering Beijing, which called the action a "severe political incident".

The US wants to put her on trial on fraud charges for alleged Iran sanctions-busting and lying to US banks about it.