The Papua New Guinea Supreme Court has ordered the Australian government to provide a resettlement plan for immigration detainees being held on Manus Island, with answers required this week.

On Tuesday, the court said a plan for resettlement of the about 900 asylum seekers being held on Manus should be offered on Thursday, after ruling in April that the Australian-government funded detention centre was illegal.

Immigration Minister Peter Dutton was contacted for comment after the ruling on Tuesday night.

Some experts and human rights groups expect the latest ruling will delay determination of the next steps for the detainees, many of whom have spent years in detention under the control of the centre operators and the PNG government.