PARIS (AFP) - Canadian Prime Minister Justin Trudeau on Thursday (May 16) called the arrest of two Canadians in China "unacceptable" and vowed to stand up to Beijing over the detentions.

"We will consistently and always stand up for Canadians, particularly these Canadians who have been arbitrarily detained," he told a news conference in Paris after China said it had formally arrested the pair on national security grounds.

"What we are always focused on is doing things that will help Canadians (who are) being detained. That will not change," Trudeau said, when asked if he planned to talk to President Xi Jinping over the issue.

Former diplomat Michael Kovrig is "suspected of collecting state secrets and intelligence" while businessman Michael Spavor is suspected of "stealing and illegally offering state secrets" abroad, Chinese foreign ministry spokesman Lu Kang said Thursday.

"The Chinese government is not following the same kind of rules that the large majority of democracies follow," Trudeau told reporters at the Canadian embassy after holding talks with President Emmanuel Macron in Paris.

"We will continue to defend these Canadians and we will continue to say clearly to China that its actions are unacceptable," he added.

Though no link has been officially made, the detention of Spavor and Kovrig is thought to be in retaliation for Canada's December 1 detention on a US extradition request of Meng Wanzhou, a top executive of Chinese telecom giant Huawei who is accused of violating Iran sanctions.