Immigration Minister Peter Dutton must immediately clarify the status of medical care available to people seeking asylum on Manus Island.

"We are hearing that there are no doctors working today in the detention centres on PNG due to International Health and Medical Service failing to properly register its medical practitioners with the Papua New Guinean government," Greens Immigration spokesperson Senator Nick McKim said.

"If this is true, Mr Dutton must take urgent action to ensure proper medical care is available to people who remain Australia's responsibility."