'Do They Want 1.4bn Chinese To Write To Trudeau?'

China on Tuesday lashed out at a group of former diplomats and academics who signed an open letter to President Xi Jinping calling for the release of two Canadians detained on national security grounds.

Foreign ministry spokeswoman Hua Chunying called it a "great disrespect" that also interferes with China's sovereignty and judicial process.

"It is a call to exert pressure, to demand the Chinese side to release two Canadian citizens who have been investigated by the relevant departments according to the law," Hua told a regular press briefing.

"Do they want China's 1.4 billion people to sign an open letter to the Canadian leader?"

Former diplomat and Hong Kong-based Michael Kovrig and businessman Michael Spavor were on December 10 arrested for activities that "endanger China's national security" – a phrase often used by Beijing when alleging espionage.

Their detentions are thought to be in retaliation for Canada's arrest on a US request of Huawei chief financial officer Meng Wanzhou, who is facing fraud charges linked to violations of Iran sanctions.

On Monday, Canada's ambassador to the US David MacNaughton said Washington will be formally requesting Meng's extradition, the Globe and Mail reported.

Hua called on both countries to drop the case, saying Meng's arrest was a "serious mistake".

"It is not an ordinary criminal case. It's an abuse of the bilateral extradition treaty between the United States and Canada," Hua said. (AFP)