Few people can claim to have sipped cocktails on board North Korean leader Kim Jong-un's private yacht, but Michael Spavor is one of them.

The Canadian businessman, who has longstanding ties with Pyongyang, has been detained in China and is being investigated on suspicion of harming its national security.

His disappearance comes amid escalating tensions between China and Canada, after the latter arrested a Chinese businesswoman at the request of the US.

Mr Spavor is the second Canadian to be detained in China this week. Former diplomat Michael Kovrig was arrested in Beijing on Monday under similar circumstances.

But Mr Spavor's close ties to North Korea, which is an ally of China, only adds to the intrigue surrounding this growing diplomatic feud.

He runs an organisation called the Paektu Cultural Exchange, which promotes tourism and investment into North Korea.

He facilitated the well-publicised and unlikely friendship between Mr Kim and the American basketball star Dennis Rodman.

Mr Spavor arranged for the pair to meet in 2013, describing the visit as a "blast".

"That was the most amazing experience I've had in my life... we hung out for three days," he told Reuters news agency last year.

Images taken at the time, and shared on social media, show Mr Spavor drinking long island iced teas with Mr Kim after going jet-skiing near the port city of Wonsan.

His organisation has also arranged lower-profile tours of North Korea on behalf of groups such as students and interested Chinese investors.

A key part of his work, according to his website, has been to promote foreign investment into the country.

"We achieve this goal by connecting interested individuals and groups with our extensive network of contacts within [North Korea]," the Paektu Cultural Exchange website reads.

In practice, this means taking delegations of investors to North Korea and introducing them to potential business partners.

"There has been a definite surge of interest among my North Korean partners in doing business across the border," Mr Spavor told the Asia Times earlier this year.

"I have been working with Chinese and Chinese-Korean investors, they are now very interested," he added.

The website reports that Mr Spavor has received enquiries from German, Canadian, British, Italian, Taiwanese and Singaporean companies about investing in North Korea.

A fluent Korean speaker, he is based in the Chinese city of Dandong which borders North Korea.

In fact, it is so close that it is possible to swim from the city's waterfront to the North Korean side of the Yalu River in a matter of minutes.

From here, Mr Spavor says he felt the rumble of one of North Korea's nuclear tests while eating brunch last September.

"It lasted for about five seconds. The city air raid sirens started going off," he told Reuters at the time.

He has also lived in Pyongyang, where he served as the managing director of a Canadian non-governmental organisation that was based in the city.

But it is his close personal ties to the North Korean government, rather than his geographic proximity, that has allowed him privileged access to the country.

In February, he was granted access to a large military parade in Pyongyang despite the fact that most foreign media had been barred from attending.

He uploaded videos to his Twitter and Instagram accounts which showed that he was in a prime position throughout the event.

Despite his closeness to the North Korean regime, which has an extensive record of human rights abuses, Mr Spavor has been reluctant to discuss politics.

"I'm really in no position to comment on political and human rights issues," he said in a 2013 interview. "Those issues are better discussed between governments."

In his most recent social media posts, he said that he would be arriving in Seoul on Monday for "consulting work" and invited friends to meet him for drinks.

But he never arrived, and those same friends are now sending Mr Spavor public messages of support following the news that he has been detained.