By Phil Mercer BBC correspondent in Sydney

Six asylum seekers have escaped from the troubled Woomera detention centre in Australia.

Immigration authorities have said guards were attacked and injured in the break-out.

Woomera was the scene of a mass break-out last March

It is claimed the escape was organised by a group of activists wearing balaclavas. The group tore down part of a perimeter fence at the remote desert facility before disappearing with the asylum seekers.

Australian police said this was a well-planned escape.

It is believed two groups travelling in separate vehicles helped the detainees break through security fences in the middle of the night.

Hunt under way

The Immigration Minister Philip Ruddock said two guards were hurt.

One was hit about the legs with a tyre lever, while another was struck in the chest.

Six asylum seekers are now on the run. Roadblocks have been set up on the Stuart highway, which links Port Augusta to the south and Coober Pedy to the north.

Woomera is a former missile testing base and lies in the heart of the South Australian desert.

Harsh conditions

There is speculation the fugitives may have gone off the main roads to evade capture and are attempting to negotiate rugged terrain in extremely hot summer temperatures.

Senior police officers have expressed grave concerns that the group may not be equipped to survive the harsh desert conditions.

The Immigration Department has said the detainees were from Afghanistan, Iran and Iraq.

The detention centre at Woomera has been in use since 1999.

It has a turbulent history, one peppered with mass escapes, riots and hunger strikes carried out in protest at Australia's mandatory detention of asylum seekers.

The government defends its policy of detaining asylum seekers on health and security grounds.

The camp at Woomera is slowly being decommissioned.

Many of its detainees have been transferred to the new Baxter facility near Port Augusta, 300 kilometres north of Adelaide, where many are facing deportation.