SYDNEY (Reuters) - Australian Prime Minister Scott Morrison said on Friday Canberra has yet to establish the whereabouts of an Australian man missing in North Korea for several days.

Australian student Alek Sigley is seen in this undated photo obtained on June 27, 2019. AAP Image/Supplied by the Sigley family/via REUTERS

The family of Alek Sigley said on Thursday they had not heard from the 29-year-old university student in Pyongyang, the North Korean capital, since Tuesday.

Sigley, who also runs a small tour company specialising in educational trips to North Korea, was an active social media user before abruptly ceasing all communication on Tuesday.

“Our key focus is to ascertain precisely where Alek Sigley is and in what circumstances,” Morrison said in the western Japanese city of Osaka, where he is attending the G20 summit of world leaders.

“It’s very concerning, I’m very concerned,” he said.

Sigley’s family said in a statement it was unusual not to have any digital contact from him.

Australia has no diplomatic presence in North Korea and relies on third-party countries such as Sweden to act on its behalf. Australia’s foreign affairs department said it has received a report that a citizen had been detained in North Korea.

Sigley, from the western Australian city of Perth, has been studying a postgraduate degree in modern Korean literature at Kim Il Sung University, according to his Twitter page, making him one of a handful of Western students there.

The treatment of foreign citizens, most usually from the United States, by the secretive North has long been a contentious issue. Some have been held as prisoners for years.

The death of American student Otto Warmbier in 2017 after he was detained in North Korea for 17 months sparked a long period of tension between Washington and Pyongyang, with the United States and North Korea even trading threats of war.

Warmbier was detained in 2016 and sentenced to 15 years of forced labour for trying to steal a propaganda poster in his hotel. He was returned to the United States in a coma and died soon after.

Sigley has been an unusually active social media user for someone living in North Korea and regularly updates his social media accounts with photos and blog posts about seemingly benign subjects such as food and fashion.

His Facebook and Instagram accounts have been suspended at his family’s request, although his Twitter profile remained open on Friday.

Sigley was also a regular contributor to international media organisations about his time in North Korea, which he described in positive language.

However, friends fear that his most recent article, an upbeat report about North Korea’s restaurants, may have caught the attention of Pyongyang authorities.

“Alek published a short piece on NKNews.org, which was not critical but it is a website that is critical of North Korea and has many sources from North Korean defectors,” said Sigley’s friend Leonid Petrov, a professor of Asian Studies at the Australian National University.

“This may have convinced North Korea that Alek was a journalist,” he said.

Chad O’Carroll, CEO of NKNews publisher the Korea Risk Group, said in a statement Sigley was a knowledgeable observer of North Korea and that the publication was surprised by reports of his sudden detention.

“We sincerely hope a rapid release can be secured by relevant authorities,” O’Carroll said.