The party, made up of seven Australians, one New Zealander, an Australian guide and local porters, was attacked late yesterday afternoon on the Black Cat Track in Morobe province.
Two porters were killed and several others in the party were injured.
Ms Plibersek has offered her deepest sympathies to the family and friends of those who died.
She says the Australian High Commission in Port Moresby is providing consular support to the Australians.
Our PNG correspondent Liam Fox gave these details to Eleanor Hall.
Presenter: Eleanor Hall
Speaker: PNG correspondent Liam Fox, Stanly Komunt from Morobe Mining Join Venture camp
FOX: Well it appears it was the porters who bore the brunt of the attack, they have some very serious injuries, two porters were killed. The Australians and also one New Zealander trekker was there as well. They were injured, we've been told that it was in the nature of lacerations, cuts and bruises and things like that. The Foreign Affairs department says that their injuries are not life threatening. After the attack they were taken to the town of Wau, which is at one of the Black Cat where they were given treatment at a camp run by the Morobe mining joint venture. I was able to speak to Stanley Komunt from the Morobe mining joint venture who was there when the Australians and the New Zealander were brought into Wau yesterday afternoon. He says they appear to be traumatised but they were ok after some treatment.
KOMUNT: Obviously traumatised and a few injuries, and once they were done they looked ok, they were talking, they were walking, having tea, so they were all good, a couple got injured, they were treated and they all retired back to the house.
FOX: And what have you been able to hear or what did they say about what happened with the attack?
KOMUNT: About three or four in the darkness they were attacked by this group, and obviously it was night, it was a pop gun and a rifle, they couldn't tell. And yeah they just took their stuff and chopped up the porters and it was all happening so fast, and they were confused as well.
HALL: That's Stanley Komunt from the mining joint venture where the trekkers were brought after that attack. Liam, what do you know about who was responsible for this, and any suggestion about a motive for the attack?
FOX: Those details are unclear at this stage. Local police have declined to comment and directed our inquiries to the police commissioner here in Port Moresby, who's also been unavailable for comment. You'd have to imagine though given the isolated area where these people were that it was locals, people from that area, and there have been some different theories floating around for the motivation. One of those is that there has been some tension between the locals along the Black Cat Track and porters who come from other areas of Morobe province. Locals feel that those sorts of jobs should be given to them because it's their area. And the other theory that it was simply a crime of opportunity, and that some local bandits, thugs or criminals have seen this party trekking and decided they'd attack and rob them.
HALL: Have there been any recent similar incidents?
FOX: No not that we're aware of. We have heard of tension between locals along the lines of what I mentioned before, tensions between locals who are on popular walking tracks and workers who come from other areas. We have heard in the last few years that sometimes it's led to some minor conflicts. But no expatriates, no tourists have been involved.