There has been another night of violence at one of Australia's controversial camps for illegal immigrants. Authorities at the remote Woomera detention center say the rioting was an attempt at a break-out by hundreds of detainees.

Hundreds of detainees at Woomera bombarded guards with stones and steel furniture. Some of the asylum seekers in Australia's biggest and most isolated detention camp attacked a perimeter fence until extra security arrived. Many buildings inside the compound have been destroyed by fire in the past few days.

Early Wednesday, authorities described the situation as calm, but the center remains on high alert.

Refugee advocates say the unrest is part of the growing frustration among asylum seekers about the time authorities take to decide whether they can stay in the country. It can take years for an asylum request to be settled.

Australia's acting immigration minister, Attorney-General Daryl Williams, said the government will not change its policy of locking away illegal immigrants until their applications are processed.

Mr. Williams says all asylum seekers are treated fairly in accordance with international law. "They are given the benefit of processing under the refugee convention," he said. "If they fail to qualify under that they are the subject of detention that's a policy the government intends to continue."

The government accuses the rioters of trying to pressure it to grant them visas to stay in Australia. Immigration officials say many of those involved in the violence are awaiting deportation after their asylum applications failed.

Refugee campaigners say many of the problems at Woomera are a result of its remote location in a barren area in South Australia. One advocate says in that environment, many detainees simply lose hope.

Human rights group Amnesty International wants an inquiry into Australia's policy of mandatory detention of asylum seekers, including women and children.