The United Nations refugee agency says it will talk to the three detainees on the roof of Sydney's Villawood Detention Centre if they come down.
Negotiations between the three men and officials remain unsuccessful in coaxing the detainees off the roof.
The men have been on the roof for six days.
A Canberra spokesman for the United Nations High Commissioner for Refugees (UNHCR) said its role was to monitor Australia's obligations as a signatory to the 1951 Refugee Convention.
"To this end, UNHCR is available via its Canberra office to provide information or discuss any grievances or concerns that any asylum seekers or refugees in Australia may have," a UNHCR Canberra spokesman told AAP on Monday.
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"However, our officials are unable to undertake discussions with individuals who are engaged in or threatening protest action, nor are they able to make guarantees on the outcomes of asylum claims which are assessed through DIAC (Department of Immigration and Citizenship) procedures."
A refugee, according to the Convention, is someone who is unable or unwilling to return to their country of origin owing to a well-founded fear of being persecuted for reasons of race, religion, nationality, membership of a particular social group, or political opinion.
The spokesman said Australia's Department of Immigration and Citizenship had procedures for assessing the protection needs of people, including access to appeal and reviews. The three men have been protesting since Wednesday.
A riot involving 100 detainees left nine buildings at the centre gutted by fire on Wednesday night. Twenty-two of the alleged rioters were taken to Silverwater jail in western Sydney.
Majid Parhizkar, 24, from Iran, and stateless Kurdish men Mehdi and Amir, whose applications for asylum have been twice rejected, are refusing to come down from the roof.
The UNHCR spokesman said it hoped the situation at Villawood was resolved as quickly as possible for the safety and welfare of all involved.
Hundreds march for detainees rights
Hundreds of refugee supporters gathered today outside Sydney's Villawood Detention Centre to support three detainees protesting on the rooftop.
However, the centre's other detainees were in lockdown, unable to communicate with the crowd.
The supporters marched the two kilometres from Chester Hill Railway Station, in Sydney's southwest, to the detention centre to show their solidarity with those on the other side of the fence.
"Freedom," they chanted, and the cry was returned by the men on the roof.
Majid's brother Hadi, 25, has been camping outside the detention centre since Thursday and says he is worried about his brother, who has been without food since the protest began.
"It's not good, he's very hungry and they can't resolve the problem," Hadi told reporters at the scene.
"It's dangerous for him and I want (him to come down).
"We came to Australia together two years ago and I was accepted after six months and Majid has not been and we want to know the reason."
His brother could not go back to Iran because he might be killed for converting to Christianity, Hadi said.
Majid felt as if he had nothing to lose and if he came down from the rooftop he might be sent to jail or be deported, he said.
The refugee supporters maintained a one-minute silence for Anzac Day, as police and detention centre security guards closely monitored the area.
