Prime Minister Scott Morrison says he prayed for the safe return of Australian man Alek Sigley who remains missing in North Korea.

A week since the 29-year-old Perth tour guide last contacted friends or relatives, Mr Morrison said he was unable to shed any light on his whereabouts.

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"I'm seeking and receiving regular updates. But this morning, in the absence of those and indeed regardless of that, prayer is my response."

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The prime minister made the comments outside a Canberra church after a service to mark the re-opening of Parliament.

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"This is a troubling situation and concerning situation and we will be continuing to use every effort that we have to locate him and hopefully bring him home safely," Mr Morrison said.

Mr Sigley, who was living and studying in the hermit kingdom and speaks Korean fluently, has not communicated with relatives or used his social media accounts since Tuesday morning last week. His family says it's very unusual for him to be out of contact.

Mr Morrison spoke directly to Mr Sigley's family last week from Osaka where he was attending the G20 summit.

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He also discussed the matter with other G20 leaders, who he said offered cooperation and assistance.

The Department of Foreign Affairs have been providing consular assistance to Mr Sigley's family.

Australia does not have a diplomatic presence in North Korea, but is working with the Swedish government which has an embassy in Pyongyang.

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There are fears Mr Sigley, believed to be the only Australian living in North Korea, has been detained, but authorities have been unable to confirm that.

- Additional reporting by AAP