Hundreds of asylum-seekers have taken part in protests at an Australian immigration detention centre in Papua New Guinea's Manus Island, with many swallowing razor blades, washing powder and sewing their lips in protest against detention.

Refugee advocate, Ian Rintoul, said on Friday that up to 40 men had sewn their lips together, three others had swallowed razor blades and four had consumed washing powder.

There were also reports that more than 400 people were on hunger strike.

Australia's Immigration Minister, Peter Dutton, confirmed a "number of incidents of self-harm within Manus," adding he was worried about the "volatile situation" at the camp.

Australia sends asylum-seekers who try to enter the country by boat to offshore detention centres on Papua New Guinea and Nauru in the Pacific with no prospect of being settled on the mainland, even if they are genuine refugees.

An asylum-seeker at Manus, told the Australian Broadcasting Corporation, there were also clashes involving security guards and detainees were threatened.

"They threatened the boys. They told them tomorrow... the new group will come from Australia and we will come and will enter into the camp and we will beat you," ABC reported.

Papua New Guinea's government, however, denied the reports on Saturday. "There was no physical engagement between asylum seekers and security personnel," a government spokesman said in a statement.

'Harsh facility'

The protests come a month before the first anniversary of a riot at the camp, which left 23-year-old, Reza Barati dead, and 69 injured after tensions flared among inmates about their fate.

The violence was described in a parliamentary report in December as "eminently foreseeable" and mostly caused by delays in processing refugee claims.

Some 1,035 men are held on Manus Island, according to latest immigration figures, while 895 asylum-seekers, 596 men, 164 women and 135 children are held on Nauru.

The UN refugee agency has condemned Australia's camps on Manus and Nauru as "harsh" facilities that "impact very profoundly on the men, women and children housed there", and asked for information from the government, warning that Australia could be breaking international law if it is forcing boats back to Indonesia without proper regard for safety.

Hundreds of people are known to have drowned making the perilous journey to Australia, fleeing conflicts in Syria, Afghanistan, Pakistan and Somalia.