Australian Prime Minister Scott Morrison said that he had no news on the fate of an Australian citizen since he vanished in North Korea a week ago.

According to the Associated Press(AP), Morrison said on Tuesday that he had prayed for 29-year-old student Alek Sigley, who has not contacted his family and friends on social media since last Tuesday.

The prime minister told reporters outside a Catholic church in the Australian capital of Canberra that it's a very troubling and concerning situation and that his country will continue to use every effort to locate Sigley and bring him home safely.

The AP said that Morrison was offered help to find Sigley by several world leaders who attended the Group of 20 summit in Japan last week.

Some media reports have speculated that Sigley, a Pyongyang University student and tour guide, had been detained. 

Meanwhile, the North's official Korean Central News Agency reported that a Swedish special envoy arrived in Pyongyang on Monday.

Australia has diplomatic ties with North Korea but does not have an embassy in the country and the Swedish embassy in Pyongyang provides consular assistance for Canberra.