On Monday, former diplomat Michael Kovrig was also detained, by the Beijing state security bureau, and faces the same accusation. Kovrig is a senior adviser for Northeast Asia with the International Crisis Group.

Chinese foreign ministry spokesman Lu Kang said the Canadian embassy in China had been notified of both cases, and the legitimate rights of Kovrig and Spavor had been protected.

“China is taking action in accordance with the law,” Lu said in a daily press briefing on Thursday.

But he declined to say whether the investigations were retaliation for the arrest of Huawei Technologies chief financial officer Sabrina Meng Wanzhou, or if they were related to North Korea.

The confirmation came after Canadian Foreign Minister Chrystia Freeland said a second Canadian citizen could be in trouble in China.

Canadian foreign ministry spokesman Guillaume Berube said Canada was working hard to ascertain Spavor’s whereabouts and would continue to raise the issue with the Chinese government.

Kovrig and Spavor know each other because of mutual interest in Northeast Asia.

Spavor is a prominent North Korea watcher and a founder of NGO Paektu Cultural Exchange. He has visited North Korea many times with delegations to assess business opportunities in the hermit kingdom.

He met North Korean leader Kim Jong-un in 2013, and joined a North Korean military parade in February this year, posting a video to his Twitter account.

He also helped arrange a visit to North Korea by former basketball player Dennis Rodman.

Spavor was set to attend a conference in Seoul at the Royal Asiatic Society on Tuesday night, but never arrived at the conference, according to people familiar with the matter.

“[We] haven’t heard from him … He never showed up. Other than that I haven’t heard anything and know nothing of his whereabouts,” one source said.

“He was supposed to be in Seoul but nobody has seen him,” another source confirmed.

Kovrig held for alleged activity that ‘endangered national security’

Canadian officials said they were officially informed of Kovrig’s detention via fax early on Monday.

“Canada is deeply concerned about the detention of Mr Kovrig and Canada has raised the case directly with Chinese officials,” Freeland, the foreign minister, said.

The Chinese foreign ministry said the International Crisis Group was not registered in China, and might have violated the country’s foreign NGO law if it carried out activities inside China.

A spokesman for the group on Thursday said it opened an office in China in 2007 after consultations with the foreign ministry, but closed its Beijing operation in December 2016 because of the NGO law.

“Michael Kovrig has been working from Hong Kong, which is not subject to the same law,” the spokesman said.

Why Huawei and its CFO are caught up in the US-China trade war

Friends and observers said that both Spavor and Kovrig might have become “hostages” and “pawns” in the trilateral tensions.

Some Canadians in mainland China said they were concerned about the diplomatic feud.

“As a Canadian who is not affiliated with the media, international relations or any other activity that would draw attention from the Chinese government, my feelings of personal safety are the same as prior to the incidences,” one Canadian working in China said.

“I am, however, concerned with where this diplomatic feud will escalate to, the future of relations between the two countries, and what that means for Canadians living in China.”

Zhang Baohui, director of the Centre for Asian Pacific Studies at Lingnan University in Hong Kong, said Meng’s arrest had angered Beijing and the developments could be a manifestation of China-US rivalry.

“This is all shrouded in secrecy so it’s difficult to know the real reasons for the arrests … in the next few days more explanations from the Chinese government will emerge regarding the detention of these Canadian citizens,” Zhang said.

Additional reporting by Bloomberg, Agence France-Presse, Reuters