Australian detainees torch buildings

Detainees carrying out a rooftop protest at Villawood Immigration Detention Centre in Sydney's southwest say they are not planning any further violence.

However, the mood at the centre remained tense, with one detainee threatening suicide and others claiming they will protest for at least one further night.

Up to 100 detainees ran amok at the centre in the early hours of Thursday morning, setting fires and vandalising property.

Protesters torched an oxygen cylinder leading to an explosion shortly after 2am.

Nine buildings, including a medical centre, a kitchen and a dining room, were gutted in the blazes, which were brought under control by emergency services.

Social Justice Network spokesman Jamal Daoud said the fires were set using piles of newspapers, mattresses and lighters.

The destruction has been condemned by political leaders, while the Department of Immigration and Citizenship has foreshadowed possible criminal charges against those responsible.

At 2.30pm there were six men sitting on a roof at the detention centre, including one Iraqi, three Kurds and two Iranians.

They claim they are being denied food and one man, a Kurd, has made threats to jump off the roof.

One of the Iranian men, who gave his name as Majid, told AAP by telephone that no more violence was planned.

"No no, I don't think there will be more violence," he said.

"But we will stay here as long as it takes."

He said he expected more detainees to join them on the rooftop later in the day and further protests to be staged overnight.

Majid said he has been held at Villawood for 20 months and wishes to remain in Australia.

All six men on the rooftop have had visa applications to remain in the country rejected, Majid added.

"The feeling among us is very bad, very bad, we are very hungry, very frustrated," he said.

The protesters unfurled a banner reading: "We are not criminals, we are humans."

A group of pro-refugee campaigners were outside the detention centre, chanting and waving placards in support.

"They (the protesting detainees) have been here, languishing, for so long it's actually the authorities that should be facing criminal charges," said Mark Goudkamp, a spokesman for Refugee Action Coalition.

Earlier, Fire and Rescue NSW denied claims water hoses were used on the detainees protesting on the roof overnight after fires broke out.

About 100 firefighters were on the scene from 20 stations in the neighbourhood to fight the blazes.

"At no stage were fire hoses pointed at any refugees on the roofs," Chief Superintendent Marcus Barker told reporters outside the centre on Thursday.

"All our efforts were concentrated on controlling the fire and extinguishing the fire.

"I believe there's been allegations that fire hoses were pointed by firefighters and I'm here to emphasise that that did not occur."

Supt Barker declined to comment on reports detainees hurled roof tiles at the firefighters while they were battling the blaze, saying he had not worked overnight.

Another detainee, named as Melad, from Iraq, earlier confirmed one detainee had thrown roof tiles at fire crews.

"There was just one detainee that threw tiles," Melad said.

Supt Barker said there had been a number of hotspots burning inside the centre.

"We had numerous seats of fire but they've all been contained," he said.

Though it was a difficult operation none of the firefighters had been injured, he said, noting that riot police had at one stage accompanied them into the compound.

Immigration Minister Chris Bowen said detainees involved in protests at Villawood risked having their claims denied if they hadn't already been rejected.

"I will be applying the character test to those who may have been involved in this incident and I will be applying it vigorously," he told reporters in Newcastle.

Protests at the centre were triggered after two men climbed onto the roof early on Wednesday.

The Villawood incident will be investigated as part of an existing independent review into violent protests that occurred at the Christmas Island immigration detention centre in March.

- AAP