Five Australians arrested after illegally landing a light plane in Indonesia's Papua province were charged with immigration offences and face seven years' jail, police said.

The two women and three men, including the pilot, were arrested when they made an unannounced landing at Mopah airport in Papua's Merauke district on September 12, after a flight from northeastern Australia.

"The five Australians have been named suspects. On Friday, we submitted their case file to the prosecutor's office to be processed," Papua chief detective Paulus Waterpauw told AFP.

The group said they were on a private sightseeing trip and believed they could obtain visas on arrival, according to police.

A low-level separatist insurgency has simmered in Papua since the 1960s. It remains one of the most sensitive and rugged corners of the vast Indonesian archipelago.

Journalists are barred from the province without special permits, and Papuan activists accuse the Indonesian military of widespread human rights abuses, especially around massive foreign-operated mining projects.

The five Australians, who are being held in custody in Papua, have been identified as pilots William Henry Scott Bloxam and Vera Scott Bloxam, and passengers Hubert Hofer, Karen Burke and Keith Mortimer.

They have been fined 28.6 million rupiah ($A3,625) for making an illegal flight in Indonesian territory.