CANBERRA--Australia's prime minister said on Friday he remained concerned for an Australian student who is uncontactable in North Korea and has been offered international support to find him.

Prime Minister Scott Morrison said the plight of Alek Sigley had been raised with him by world leaders attending the Group of 20 summit in Osaka, including Prime Minister Shinzo Abe.

"We're talking to our partners in that part of the world to get to the bottom of what has occurred here," Morrison told Nine Network television.

"It's obviously very concerning. I'm very concerned about it. We've had a lot of sympathy also expressed and willingness to assist by other countries," he added.

Morrison, who dined with U.S. President Donald Trump on Thursday night, declined to say which government leaders he had discussed the disappearance with and what help had been offered.

Australia has diplomatic ties with North Korea but does not have an embassy there. The Swedish Embassy in Pyongyang offers limited consular help to Australians.

Sigley, a 29-year-old Pyongyang university student and tour guide, has been out of contact since Tuesday and some media reports say he was detained. Official media in North Korea haven't mentioned an arrest.

His Japanese wife Yuka Morinaga, 26, said she usually speaks to him daily by WhatsApp from her home in Tokyo, but had not heard from him since Monday.

Morinaga, a software developer who married Sigley in a lavish ceremony in Pyongyang last year, told News Corp. she was "very concerned."

"We don't know what's happened," Morinaga said. "We don't even know if he's been detained or not."

"Some people might say he's naive because he's very pure and believes in ... doing good," she added.

Sigley's family said on Friday they had shuttered his social media accounts "to limit unnecessary speculation and commentary on those channels."

"He remains out of digital contact with friends and family, and Australia's Department of Foreign Affairs and Trade continues to seek clarification as to his whereabouts and welfare," a family statement said.

"Alek's family and friends hope to hear from him soon," the family added.

Australia advises people to reconsider their need to travel to North Korea due to how its laws apply to foreigners and says foreign visitors have been subject to arbitrary arrests and long-term detentions.

North Korea has been accused in the past of detaining Westerners for slight infractions and using foreign detainees as political pawns to gain concessions. As the country pursued diplomacy with the United States last year, it released three American detainees in what the nation's propaganda described as a gesture of goodwill.

Leonid Petrov, an Australian National University expert on North Korea and friend of Sigley, suspected that the missing Australian had been "deliberately cut off from means of communications" temporarily because Trump was in the region.

"I know Alek well and he has been always on Facebook, on Skype and he is very proactive in the media," Petrov said.

"In the context of what is going on on the Korean Peninsula right now--President Trump is in Japan today, going to be in South Korea on Sunday, potentially going to the Demilitarized Zone--I believe tensions and security measures are heightened both in South and North Korea," he said.

"I think that North Koreans potentially might have decided to shut down his blog, his Facebook account because the information coming out of North Korea ... is unprecedented. Normally North Korea is a closed book," he added.