Canada and its allies are pushing back against China with their strongest diplomatic language yet, accusing Chinese authorities of detaining two Canadians without cause and calling for them to be promptly freed.

"We are deeply concerned by the arbitrary detention by Chinese authorities of two Canadians earlier this month and call for their immediate release," Foreign Affairs Chrystia Freeland said in a statement released this afternoon.

"I wish to express Canada's appreciation to those who have spoken recently in support of the rule of law as fundamental to free societies. We share with our partners the conviction that the rule of law is not a choice: it is the bedrock of democracy. Canada will not compromise nor politicize the rule of law and due process."

Freeland's call was quickly followed by the United States issuing its own statement, which said that "Canada respects its international legal commitments by honouring its extradition treaty with the United States."

"We also express our deep concern for the Chinese Government's detention of two Canadians earlier this month and call for their immediate release," Robert Palladion, deputy spokesman for the U.S. Department of State, said in the statement.

Earlier this month, Canada arrested Meng Wanzhou, the chief financial officer of the Chinese telecom giant Huawei, at the request of U.S. officials who accuse her of violating trade sanctions on Iran. Meng has since been released on bail pending extradition proceedings.

Not long after Meng's arrest, Chinese officials confirmed that two Canadian men had been detained in China on national security concerns.

One of the two men, Michael Kovrig, served as a diplomat with GAC but was on leave to work with the International Crisis Group, a non-governmental organization, at the time of his arrest. The other, Michael Spavor, is a businessman who arranges tours of North Korea.

A third Canadian, Alberta teacher Sarah McIver, was detained in China earlier this week and was sentenced to administrative punishment for working illegally in the country, according to China.

Prime Minister Justin Trudeau said earlier this week that he'd seen no indications that McIver's arrest was related to the detention of Spavor and Kovrig.

Ministers, PMO put on alert

According to a government source, Canada's statement came after Trudeau held a meeting earlier today with senior officials involved in the case. On the call were Defence Minister Harjit Sajjan, Public Safety Minister Ralph Goodale, Freeland, Trudeau's National Security and Intelligence Adviser Greta Bossenmaier and other senior PMO staff.

The conversation focused on Spavor and Kovrig and the attempts being made to make sure their safety and human rights are respected. The meeting also addressed the arrest of Meng and efforts to reach out to Canada's allies.

The source said that Freeland spoke by phone earlier today with the Chinese ambassador to Canada and U.K. Foreign Secretary Jeremy Hunt, adding that Freeland was also reaching out to European allies.

All of the people who were a part of the meeting today have been told that they will be on alert over the holiday period should they need to respond to any new developments.

Allies weigh in

"The two situations are very different. The allegations of national security problems, even objectively, are very different from a routine case or a problem with a visa or something of that nature," he said.

Today, the United Kingdom and the European Union issued statements of their own backing up Canada's position.

"The U.K. has confidence Canada is conducting a fair and transparent legal proceeding with respect to [Meng], respecting the international legal commitments in its extradition treaty with the United States," said British Foreign Secretary Jeremy Hunt in a statement.

"The U.K. and Canada share a commitment to the rule of law, which is fundamental to all free societies. I am deeply concerned by suggestions of a political motivation for the detention of two Canadian citizens by the Chinese government. I call for them to be treated in a fair, unbiased and transparent manner."

Michael Spavor and former Canadian diplomat Michael Kovrig were taken into custody earlier this month in China. (The Associated Press/International Crisis Group/The Canadian Press)

The EU, meanwhile, openly questioned the legitimacy of China's legal system and the independence of international NGOs operating in China.

"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," EU spokeswoman Maja Kocijancic said in a statement. "The denial of access to a lawyer under their status of detention is contrary to the right of defence."

Kocijancic said the EU supports the Canadian government in its efforts to have Kovrig and Spavor released.

"The EU has concerns about the implementation of the NGO law and its impact on our people-to-people relations and the operations of international NGOs operating in China."