Asylum-Seekers broke out of an Australian immigration detention on Papua New Guinea's Manus Island on Sunday evening, with several injured.

Australian Immigration Minister Scott Morrison said that 35 asylum-seekers had escaped.

But they were quickly rounded up by private security contractors at the facility, one of two remote Pacific camps used in Canberra's hardline offshore immigration detention policy.

Under the scheme, aimed at deterring people-smugglers, any asylum-seeker arriving by boat or intercepted at sea is transferred to Manus or 1,400-mile-away Nauru for processing and permanent resettlement outside Australia.

Eight detainees were arrested over the disturbance and 19 sent to the medical centre for treatment.

"As of this morning, five of those transferees remained at the clinic. A number of G4S security contractor staff also sustained minor injuries," Mr Morrison said.

He claimed that security staff used "personal protection gear" and "no batons or other weapons were in-situ."

But refugee activist Ian Rintoul said several asylum-seekers had suffered broken hands and baton injuries, adding that one refugee "has 70 stitches in his head," indicating a use of force "out of all proportion."

Mr Rintoul added that the detainees now feared vigilante reprisals from islanders who oppose the Australian facility, with some inside the camp telling him that locals had armed themselves with machetes, knives and guns.

"The imposition of the detention centre on Manus Island has created local tensions from the very start," he said.

"Lack of transparency about resettlement has added to the tensions."

The breakout followed a tense meeting between detainees and officials from Papua New Guinea's immigration authority to discuss their fate if they were found to have a genuine refugee claim.

Mr Morrison said detainees "became agitated and commenced chanting" after they were informed they would be resettled in Papua New Guinea and "a third country option will not be offered."

The United Nations refugee agency has condemned the Manus and Nauru camps as "harsh" facilities that impact "profoundly on the men, women and children housed there."