The indefinite detention of asylum seekers on Nauru is ''an egregious breach of international human rights law'', says the Gillard government's hand-picked human rights commissioner, Gillian Triggs.

And in a separate development, Australia has told Sri Lanka - a country it has been returning asylum seekers to - that it must stop its police and army abusing, torturing and mistreating its citizens, and must end the disappearances and abductions occurring across the country.

Australia's demands to Sri Lanka were made in Geneva as part of the United Nations universal periodic review process, in which all UN countries have their human rights records assessed by fellow members.

Professor Triggs, who was appointed human rights commissioner in June, told Fairfax on Tuesday that she would seek an urgent meeting with Immigration Minister Chris Bowen about Nauru when she returned from a human rights conference in Jordan.

''I have made my view really plain to the Department of Immigration and Citizenship in saying that to detain people on this remote island, and delaying by at least six months their processing, and where they're advised that they will be kept there for five years, is an egregious breach of international human rights law,'' she said.

''Asylum seekers have a legal right under international law to have their claims assessed in a speedy and appropriate way, and this is at risk of being arbitrary detention.''

Meanwhile, the hunger strike on Nauru dragged into its sixth day. An asylum seeker on Nauru told Fairfax that more than 300 people were taking part in the protest, and that the men were weak, with most spending their days lying around ''and feeling the sickness''.

Doctors had told Omid, an Iranian man who has refused to eat for 27 days, that his heart was under grave pressure, the asylum seeker said.

''If you look at him, he is only bone and skin. He says it is better to die than to live in Nauru,'' he said.

The asylum seeker said an immigration official had told the group that their claims for asylum would not begin to be processed for at least six months, and that they would be on Nauru for a year.

''They will be living for the rest of their lives with the hellish punishment [of Nauru],'' the man said.

A joint parliamentary committee in February found that detention for longer than three months causes mental illness.

Greens senator Sarah Hanson-Young said the conditions on Nauru were bringing vulnerable people ''to breaking point''.

"The government is continuing to house refugees in tents despite temperatures in excess of 40 degrees, and has increased the stress at detention centres by suspending the processing of their claims for asylum,'' she said.

"This is in spite of the ever-increasing list of organisations that are slamming the government for its cruel, expensive and ineffective offshore processing regime.''

On Tuesday in Geneva Australia's delegation to the UN told Sri Lanka that it must stop its torture and enforced disappearances.

The delegation said that while it welcomed Sri Lanka's stated commitment to protecting human rights, it was important for it now ''to achieve measurable, concrete improvements".

But despite the concerns raised before the UN, Australia has sent back 125 asylum seekers to Sri Lanka since restarting offshore processing in August.

These deportations have been halted for at least a month after a Federal Court decision last week prevented the Immigration Department sending back a 42-year-old man who had failed in his bid to win refugee protection.

In July, Fairfax revealed that asylum seekers forcibly returned to Sri Lanka had faced arbitrary imprisonment, torture and harassment by security forces.

Sri Lanka's special envoy for human rights, Mahinda Samarasinghe, told the UN that his country would send a set of voluntary pledges to the UN Human Rights Secretariat within two weeks. He said Sri Lanka — which emerged from a bloody 26-year civil war in 2009 — would update the UN on postwar progress. Mr Samarasinghe said his government was concerned more than any country with "winning the peace" and building a comprehensive rehabilitation. "On many fronts progress has been achieved, but we still acknowledge, at the same time, that challenges are ahead of us," he said. "We ask our friends in the international community to give us the time and space to make further progress.

"We are working for a new Sri Lanka, we are working for a united Sri Lanka."

This year 5501 Sri Lankan asylum seekers have reached Australia, the highest annual number on record and a 26-fold increase over  last year.

Opposition immigration spokesman Scott Morrison said Sri Lankan asylum seekers should be put on a plane and deported immediately.

Britain, which also previously returned failed asylum seekers to Sri Lanka by charter flight, was last month stopped from deporting a number of Tamils after the High Court found they were at risk of torture.

■Home Affairs Minister Jason Clare said three boats bound for Australia had been intercepted near the Cocos Islands on Monday, bringing to seven the number of boats since the weekend.

He said 58 people on board the three boats would be sent to Christmas Island for health and security checks. Another 63 people on a boat that sought assistance north-west of Ashmore Islands on Monday night were rescued on Tuesday and will also be sent to Christmas Island, where there are already 2505 asylum seekers.

Nauru A 'Breach' Of Rights