Professor freed from PNG criminals returns to Australia

An archaeologist has returned to Australia after being released by armed criminals who were holding him and three others hostage in a remote part of Papua New Guinea.

Professor Bryce Barker flew by charter jet to Cairns from the PNG capital Port Moresby on Monday afternoon.

The New Zealand academic later touched down in his home city of Toowoomba, where he works at the University of Southern Queensland.

Prof Barker and two PNG nationals were freed on Sunday after reportedly being held at gunpoint by 20 armed men in PNG's Southern Highlands, according to a local police report.

The highly regarded archaeologist and his research crew had been conducting fieldwork in the remote area when they were taken hostage by the attackers, who demanded a $3.5 million kina ($A1.4 million) ransom.

A smaller ransom was reportedly paid during hostage negotiations over the weekend.

Two separate payments were made to secure the release of the research team, the ABC reported.

PNG Prime Minister James Marape said the first stage of the police operation was complete but he said authorities would still go after those responsible.

"The police will still be in pursuit of those who engage in such horrible criminal enterprise," he told reporters on Monday.

Mr Marape called on the culprits to "turn yourselves in" so they could face a "competent court" over their alleged crimes.

"We will not rest, this is just the first phase of the operation, second phase continues, third phase continues to ensure that those who engage in criminal enterprise ... are facing the laws of the country," he said.