Australia says it is "urgent" to confirm reports that an Australian man has been detained in North Korea.
The family of Alek Sigley, a 29-year-old student living in Pyongyang, could not confirm this, but was arrested, but said he had not had any contact with them since Tuesday.
Australian officials tried to confirm his situation, his family said.
The government has described it as a "very serious situation".
Representatives in South Korea had contacted "relevant officials" in North Korea, a minister said.
"It was not confirmed that Alek was detained in the DPRK," his family said in a statement on Thursday.
"The situation is that since Tuesday morning Australian time, Alek is no longer in digital contact with friends and family, which is unusual for him."
It is not known why Mr. Sigley, an Asian scholar and fluent Korean spokesman, may have been imprisoned. His friends reported missing him earlier this week, the Australian Broadcasting Corporation reported.
Who is Alek Sigley?
Born in Perth, he has lived in North Korea for a year and holds a master's degree in Korean literature from Kim Il-sung University.
He has also run a business offering tours for Western tourists visiting the totalitarian, communist state. He visited him in 201
In March, he described himself as the "only Australian resident of North Korea" in a piece published by The Guardian.
He said he was interested in living in North Korea after meeting some citizens while studying in China.
As a foreign citizen, I have almost unprecedented access to Pyongyang with a student visa.
"I can roam the city without anyone accompanying me."
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Last year, he told Sky News that as a Westerner living in the oppressive regime, despite some high-profile cases involving foreigners, " never threatened ".
Foreigners once arrested?
Several Foreigners Arrive The Australian John Short was arrested in North Korea, sometimes for illegal entry or "enemy crimes against the state," as Pyongyang calls it.
Religious activities are severely restricted in the north, and missionaries have been arrested multiple times.
US student Otto Warmbier was imprisoned in North Korea in 2016 for stealing a propaganda badge during an organized tour.
He spent 17 months in prison and died in a coma several days after returning to the United States.
North Korea denied the mistreatment of the 22-year-old student, however, his parents insisted that he died in July 2017 the consequence of torture.
The United Nations criticized North Korea's human rights record, saying that the citizens of the totalitarian state live under "systematic, widespread and gross human rights violations".
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Nonetheless Recent historical meetings with the US and South Korea have kept North Korea isolated from the world because of tensions over its nuclear ambitions.
Like many other Western nations, Australia has no message in North Korea. It only has limited diplomatic access via the Swedish embassy.
Australian Prime Minister Scott Morrison is currently in Osaka, Japan, where he will meet other world leaders at the G20 summit.