A group of Australians who were attacked with machetes on a trekking expedition in Papua New Guinea are expected to return home today.

Seven Australians, a New Zealander and their porters were ambushed while trekking along the Black Cat Track in Morobe province on Tuesday.

Two local porters were killed and some of the trekkers were injured during the attack.

The group had set up camp for the night and were in their tents sheltering from rain when the attack happened.

Two of the Australians, Nick Bennett and Steve Ward, are both businessmen from Mackay on the central Queensland coast.

Mr Bennett was struck in the head with a machete and Mr Ward was punched several times

The injured men hiked four hours back to safety, carrying the porters' bodies.

The group were flown to Port Moresby yesterday and are expected to return home this morning.

PNG's prime minister Peter O'Neill says those responsible for the brutal attack will face the death penalty.

Mr O'Neill says the ordeal is an "obvious setback" to efforts to promote PNG as a tourist destination.

The motive for the attack is not clear, although some reports have suggested it could be related to a disagreement between porters from PNG's lowlands and locals living in the highlands.

After the Kokoda Track, the Black Cat Track is one of the most popular treks in PNG.

It is a rough track that runs from the village of Salamaua on the coast of the Huon Gulf, south into the mountains to the town of Wau.

In the wake of the attack, the Department of Foreign Affairs is advising trekkers to avoid the track until local police have investigated the incident.