Refugees and asylum seekers in Papua New Guinea have been threatened with arrest and prosecution as authorities ratchet up the pressure ahead of the closure of Australian operations on Manus Island.

Meanwhile, the Turnbull government is under pressure from Labor to "come clean" after Fairfax Media revealed a boat carrying six Chinese men and a PNG man had successfully landed in Australian territory.

The $70 million will be paid to up to 1923 asylum seekers detained on Manus between 2012 and 2014. Credit:Alex Ellinghausen

About 100 men have now been transferred from Manus Island to Port Moresby, according to witnesses, while refugees were sent a forthright letter outlining their options before the Manus centre closed on October 31.

The men were given four options: relocate to the transit centre, move into the PNG community, go home voluntarily or resettle in a third country, potentially the US. Australia's offer of $20,000 for those who go home voluntarily expires on Thursday.