This file photo taken on July 9, 2019 shows dead bodies lined up on a road in Hela province. A woman hostage, one of four people held captive by an armed group in the remote Papua New Guinea highlands, was released and negotiations are continuing for a "peaceful resolution" to the situation, the Pacific island nation's police commissioner said. (AFP PHOTO / DEPARTMENT OF HEALTH, HELA PROVINCE)

SYDNEY – A woman hostage, one of four people held captive by an armed group in the remote Papua New Guinea highlands, was released and negotiations are continuing for a "peaceful resolution" to the situation, the Pacific island nation's police commissioner said.

A group of archaeology researchers, including a professor working for an Australian university, two local university graduates and a program coordinator were taken hostage by heavily armed men demanding a cash ransom on Sunday.

A PNG Post Courier newspaper reported that a dozen of the men holding the hostages had been identified by police

The group were on a field trip to the remote village of Fogoma'iu in the Mount Bosavi region, near the boundary of Southern Highlands and Hela provinces.

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The professor is an Australian resident and New Zealand citizen, and is not being publicly identified because of the sensitivity of the situation.

"The release of one female Papua New Guinean captive is a positive outcome, and negotiations continue for the safe release of the remaining two female Papua New Guineans and the male New Zealand citizen," Papua New Guinea's Police Commissioner David Manning said in a statement late on Wednesday.

The three captives are in reasonable health but are being held in difficult terrain, he said. Communication was challenging, he added.

Police said on Monday that special security forces were travelling by air to the area and would use lethal force against the criminal gang if necessary to secure the release of the hostages. The latest police statement emphasized negotiations would be careful to avoid escalating tensions.

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Any harm to the captives would result in a swift security response, Manning warned the abductors.

The PNG Post Courier newspaper reported that a dozen of the men holding the hostages had been identified by police.

ABC television reported that another foreign man who was in the vicinity had been escorted out for his safety.