Police say they will use lethal force if necessary to secure the release of an Australian professor and three colleagues who were taken hostage in a remote area of Papua New Guinea while conducting a field study.
A special police operation is now underway to rescue the group, which consists of the Australian professor, a Papua New Guinean program coordinator, and two University of PNG graduates.
The ABC understands the professor is an Australian permanent resident, but a New Zealand citizen.
Police Commissioner David Manning described the situation as "delicate" in a statement.
"Our specialised security force personnel will use whatever means necessary against the criminals, up to and including the use of lethal force, in order to provide for the safety and security of the people being held," Mr Manning said.
Earlier, PNG's Prime Minister James Marape told reporters in Port Moresby on Monday there were "running conversations" between PNG authorities and the kidnappers.
"I just want to inform the families of those taken hostage that we have been at work and contact has been made with people in the bush," he said.
"We've got police and military on stand-by to assist. But, in the first instance, we want those criminals to release those who are held in captivity.
"We have been keeping this under close wraps because of the sensitivity and the need for us to get our friends [who were] captured, get them alive and safe."
Mr Marape indicated that missionaries who had been living in the area for a long time had been helping by acting as intermediaries with the kidnappers, and had spoken to the Australian professor by satellite phone.
"This morning there was positive news that they are alive and villagers on ground who are not involved in these criminal activities, these villagers have also been assisting in negotiations to get them out," he said.
"So I'm confident, I'm optimistic, I'm prayerful that we get … them out."
The ABC has been told that the criminal group initially also took local guides accompanying the group hostage, but later released them.
Australia's Department of Foreign Affairs and Trade (DFAT) has been contacted for comment.
The New Zealand Ministry of Foreign Affairs said it was aware of the case but could not comment for privacy reasons.
The ABC has chosen not to name the kidnapped Australian at this stage.
