Australia has tightened security at immigration detention centres across the country following a wave of violence and arson.

Riots and fires have broken out at five of the country's detention centres over the last week, causing damage that officials have put at more than A$7m (US$4m).

Refugee advocates say detainees are desperate

Fifteen inmates from Sydney's Villawood camp have been transferred to a high security prison where they face possible criminal charges over arson and an attempted break-out on New Year's Eve.

A further seven people face possible charges over arson and attacks on guards at Woomera camp in the south Australian desert.

Extra staff have been deployed at camps, while state police have also been helping to bolster security at some camps. Strip searches are to be used more widely to prevent inmates from carrying weapons, the immigration department has announced.

Australia's camps currently hold about 1,100 people, who are either awaiting to have asylum claims considered, or who are being held for visa violations.

'Desperation'

Refugee advocates say the unrest stems from desperation among migrants, who may be held for years while their claims for asylum are processed.

"Detention centres are clearly in crisis," said Louise Newman from the Royal Australian and New Zealand College of Psychiatrists.

"This is a crisis of mental health, with people showing signs of trauma, despair and breakdown."

But Attorney General Daryl Williams blamed refugee advocates for encouraging the violence.

"They appear to be actively or tacitly condoning the actions of detainees who have been engaged in violence or destruction," he said. "That encourages those detainees."

The protests first broke out at the Baxter detention camp in South Australia on 29 December. Copycat violence then spread to Woomera, Villawood, Port Hedland camp in Western Australia and a camp on the remote Indian Ocean territory of Christmas Island.

Prime Minister John Howard and his government have been criticised by human rights groups and the United Nations for its policy of detaining asylum seekers.