Police in Papua New Guinea say they have arrested three men for the alleged robbery, assault and gang rape of one of two trekkers on the famous Kokoda Track.

A British man and an American woman, both 31, were walking along the trail without an organised tour group when they were attacked on Monday.

Assistant Commissioner Sylvester Kalaut said the pair was robbed, the man was beaten and the woman raped by three local men before the tourists escaped and were helped by villagers.

"That happened on Monday morning, about eight [o'clock]. The culprits assaulted them and dragged them into the bushes and that's where the female trekker was raped," he told the ABC.

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PNG media reported on Wednesday that the suspects were apprehended by villagers who handed them over to police.

Police said the trekkers ran to a local village and were airlifted to the capital, Port Moresby, where they are undergoing medical treatment.

Earlier, Mr Kalaut told PNG's The National newspaper that the suspects, armed with bush knives and spears, ambushed the pair as they were heading towards the Templeton Two campsite.

Interviews with the American woman and British man in UK tabloid The Sun makes no mention of sexual assault, but photographs confirm deep wounds to the fingers of the female tourist which police and the victim said were from a bush knife.

A New South Wales state MP who also runs tours on the Kokoda Track, Charlie Lynn, told Pacific Beat it was a tragic event that in his opinion was entirely preventable.

Sorry, this audio has expired American, Briton attacked on PNG's Kokoda Track ( Bruce Hill )

"I've never had one single issue with villagers along the trail. They've been welcoming, they've been helpful, they like the industry, they love Australians, they love trekkers," he said.

"This is out of character, but if you go to Papua New Guinea you don't walk around the bush without a local guide."

In advice issued on Wednesday, DFAT's Smartraveller website said the pair were hiking without a licensed tour operator, and tourists should ensure they only travel with guides from reputable trekking companies.

In 2013, Australians were among those injured when robbers attacked a group trekking the Black Cat Track, leading to the hacking death of two of the group's porters.