A professor from Australia along with two colleagues were released on Sunday after being held for a week by armed men in a remote part of Papua New Guinea, Australia's ABC reported.

"It took us a while but the last three have successfully returned. We apologize to the families of those taken as hostages for ransom," Prime Minister James Marape said in a statement.

He said the hostages had been freed after "covert operations," and the original ransom demand had not been fulfilled. He did not provide more details. 

Who are the kidnapped?

The professor is a resident of Australia and a citizen of New Zealand. His colleagues are two Papua New Guinean university graduates and a program coordinator.

The French AFP news agency identified him as Bryce Barker. He was seen walking alongside his two Papua New Guinean colleagues across the tarmac at Port Moresby's airport upon the trio's release.

Geraldine Mackenzie, the vice-chancellor of the University of Southern Queensland, told AFP that Barker's Australian colleagues were "relieved" by his release. She described him as "much loved" and "highly regarded."

How were they kidnapped?

Officials said the group conducting archaeology research was taken hostage last Sunday by men, who were demanding a cash ransom.

They were traveling to the remote village of Fogoma'iu in the Mount Bosavi region, near the boundary of Southern Highlands and Hela provinces when they were captured.

This was followed by negotiations and a security operation by Papua New Guinea police and defense personnel, in collaboration with the governments of Australia and New Zealand, said ABC.

The abductors had initially demanded a ransom of US$1 million (€940,000), but later dropped the asking price and abandoned a 24-hour deadline.

A woman who was part of the group of academics had been released earlier this week.

At the time, the police said the three captives were "in reasonable health, though are being held in difficult terrain."

tg/ar (dpa, AFP, Reuters)