Protesters still on detention centre roof

Four protesters remain on the roof at Sydney's Villawood Detention Centre following a fiery riot and detainees say they want to talk to a United Nations' representative.

A riot by up to 100 detainees on Wednesday night left nine buildings gutted by fire.

Twenty-two protesters, transferred to Silverwater Correctional Centre, have been questioned by police and .

Social Justice Network member Jamal Daoud on Saturday said a handful was still on the roof, while most were contemplating their fate inside the detention centre.

"There's a few people on the roof. One of them collapsed yesterday and he decided to come down because he's epileptic," Mr Daoud told AAP.

"They're feeling very bad. At the moment, they're very depressed.

"They want to talk to a UN representative for refugees and they've said: 'If it is impossible for us to be released in the community, send us to a third country'."

A Department of Immigration spokeswoman said 22 detainees were still at Silverwater Correctional Centre and Australian Federal Police (AFP) were talking to those still on the roof.

"As far as I'm aware, there's still four (on the roof) and they're actively being negotiated with and the AFP are in charge of those negotiations," the spokeswoman said on Saturday.

The protest was triggered after two men climbed onto the roof of the main centre early on Wednesday after having their asylum applications rejected.

They were joined by another 11 and, by midnight (AEST), up to 100 people were involved, vandalising and setting fire to buildings. There was an explosion shortly after 2am on Thursday when an oxygen cylinder ignited.

Meanwhile, acting Prime Minister Wayne Swan on Saturday condemned a rally outside the centre, planned for Monday by the Refugee Rights Action Network.

Mr Swan said the rioters' actions could not be defended and the rally would be inappropriate.

"I don't think that's necessarily appropriate at all. There has been unacceptable behaviour by people inside the facility," he told reporters in Cairns.

"We cannot, in any way, condone the sorts of acts and behaviour we have seen at that facility in recent days."

Mr Swan refused to be drawn on the police's decision to deny food to the four protesters still on the centre's roof.

"I think the authorities should take every responsible course of action to remove people from those positions. That is entirely a matter for the law enforcement officials."

However, Mr Swan on Friday promised those involved would "feel the full force of the law".

But he has ruled out making any changes to Australia's immigration detention policies until after an inquiry is completed into the Villawood riots and a similar incident last month at the Christmas Island detention centre.

- AAP