Canada, supported by its allies, called on China to release two Canadians who have been detained in what is widely seen as retaliation for Canada’s arrest of a top Chinese tech executive, pending extradition to the United States.

“We are deeply concerned by the arbitrary detention by Chinese authorities of two Canadians earlier this month and call for their immediate release,” Canadian Foreign Minister Chrystia Freeland said on Friday, according to Associated Press.

A senior Canadian official said China’s ambassador to the country was called, also on Friday, and informed of Canada’s demand, AP reported.

Friday’s action was Canada’s first formal demand for the release of its two citizens. The demand marks an escalation from Ottawa, which has thus far remained mum – an approach which has earned Canadian Prime Minister Justin Trudeau criticism from the opposition.

The EU, UK and US also issued statements in support of Canada’s stance.

There was no immediate response from Beijing.

Undiplomatic tit-for-tat

On December 1, Meng Wanzhou, the chief financial officer of telco Huawei – arguably, China’s flagship company – was arrested in Canada at the request of the United States. Washington seeks her extradition to face charges that she and her company misled banks about Huawei’s business dealings with Iran, which the US sanctions.

Nine days later, Beijing detained two Canadians expatriates in China: analyst Michael Kovrig and self-employed Michael Spavor, who engages in consulting on North Korea. They were accused of “activities that endanger the national security” of China.

Freeland said that that Canada was honoring its extradition treaty with the United States and that it was conducting a fair and transparent due process with regard to Meng’s case.  Meng, after a process attended by lawyers, has been released on bail, pending further proceedings, and is reportedly residing at her luxury home in Vancouver.

Meanwhile, according to the Washington Post, Kovrig is being detained in a cell with 24/7 lighting, and has been denied access to a lawyer. There is no information on Spavor, though both he and Kovrig have been visited by a Canadian consul.

Western allies raises voices

With the situation now in its third week, Canada’s allies have stepped into the breach.

The EU issued a statement reading, “The declared motive for the arrest and detention of Michael Kovrig and Michael Spavor, both Canadian nationals, raises concerns about legitimate research and business practices in China.”

UK Foreign Secretary Jeremy Hunt said in a statement that he is “deeply concerned” that Beijing may have detained the two Canadians for political reasons.

US State Department spokesman Robert Palladino reiterated that Canada is honoring its extradition treaty commitments. “We also express our deep concern for the Chinese Government’s detention of two Canadians earlier this month and call for their immediate release,” US State Department spokesman Robert Palladino said.

The detention issue has arisen at a time of high tensions between Beijing and Washington, which are engaged in an undeclared trade war.