A second Canadian citizen is being held in China on suspicion of endangering national security, adding to tension after Canada's arrest of a top Chinese telecom executive on a US request.

Michael Spavor, a China-based business consultant who facilitates trips to North Korea, was placed under investigation on Monday by state security in the northeast city of Dandong, the official Liaoning province news agency said.

His disappearance emerged after former Canadian diplomat Michael Kovrig was detained by state security during a visit to Beijing. That also occurred on Monday and was under similar suspicions.

Mr Kovrig's arrest was seen by experts as retaliation over Canada's arrest of Meng Wanzhou, the chief financial officer of Chinese telecom giant Huawei, in relation to breaking Iran sanctions.

Mr Spavor is suspected of "engaging in activities that harm China's national security", the Chinese news agency added.

Based in Liaoning province, which borders North Korea, he has met North Korean leader Kim Jong-un and famously arranged some of retired NBA star Dennis Rodman's visits there.

The Canadian government had earlier reported that Mr Spavor was missing in China after being questioned.

Chinese police stand outside the Canadian embassy in Beijing

The Beijing News daily has reported that Mr Kovrig, who works for the International Crisis Group think tank, was under investigation on suspicion of "engaging in activities that endanger China's national security," - a phrase often used in espionage cases.

Ms Meng was released on bail by a court in Vancouver on Tuesday pending a US extradition hearing.

Her case has infuriated Beijing and shaken Canada's relations with China.

Mr Spavor is based in northeast China, where he runs the Paektu Cultural Exchange programme, an organisation that facilitates sport, cultural, tourism and business trips to North Korea.

He earned recognition after helping facilitate visits by former Chicago Bulls star Rodman in 2013 and 2014. Mr Spavor has also appeared in North Korean state media photos showing him talking with Mr Kim a few years ago.

"We have been unable to make contact since he let us know he was being questioned by Chinese authorities," Canadian foreign ministry spokesman Guillaume Berube said.

Foreign Minister Chrystia Freeland said the Canadian government had raised his case with Chinese authorities.

Mr Kovrig's fate is also unknown, as Chinese authorities have yet to confirm why he is being held.

His employer, the Brussels-based International Crisis Group, said he was detained by the Beijing bureau of Chinese state security Monday night, but it has not received any information since then.

China's foreign ministry spokesman Lu Kang said yesterday that ICG was not registered in China and its employees would be "in violation" of the law if they engage in activities in the country.

Canadian officials said they were officially informed via fax early yesterday of Mr Kovrig's detention.

ICG closed its office in the Chinese capital after Beijing passed a law on NGOs, which came into force in 2017, to better control the activities on its soil of foreign organisations.