Australia's Prime Minister John Howard says disturbances at detention centers will not change the government's immigration policy. Millions of dollars worth of damage have been caused at camps housing asylum seekers in South and Western Australia in recent days.

Late Tuesday afternoon, Australian authorities reported that asylum seekers had set fire to buildings at a detention center on Christmas Island. It is the fourth facility to be set alight since Saturday. Earlier Tuesday, firefighters needed more than four hours to control fires at Woomera, a remote detention facility in the South Australian desert.

The fires at Woomera and Christmas Island follow a series of fires Saturday and Sunday at two other camps housing illegal immigrants.

Prime Minister John Howard says the detention centers face serious unrest but he says the situation is not out of control. He says the government will not change its tough stance on illegal immigrants. "To those refugee advocate groups who think this is a reason for changing policy, can I say they're mistaken," he saysl "It is not."

Immigration officials say no one was injured at Woomera, although staff members were forced to flee when detainees attacked them with rocks and metal pipes.

Australia detains all asylum seekers who attempt to enter the country without proper documentation while their applications for refugee status are processed. Human rights activists and the United Nations criticize the policy as inhumane. The government says the policy is necessary on health and security grounds.

Refugee advocates say the recent disturbances are not surprising given the frustration detainees feel. Paul Boylan, from the Woomera Lawyers Group, says the protests are probably triggered by desperate people who have been unfairly treated by immigration authorities and whose futures are bleak. Many of the detainees thought to be involved in the protests have had their applications to stay in Australia rejected and face deportation.

Australia accepts about 10,000 refugees a year, after their claims for asylum have been processed at refugee camps outside the country.