Australian authorities have seized a boat carrying 140 suspected illegal immigrants from Iraq.

The fishing boat was intercepted 1,400km off Australia's west coast and escorted to Christmas Island, an Australian-administered territory close to Indonesia.

Immigration officials say the appearance of so many Iraqis remains a mystery, but believe they were trying to immigrate illegally to Australia after leaving from Indonesian territory.

The Iraqis are thought to be the largest group of would-be illegal immigrants ever seized by Australia on board one vessel.

In June, Australia announced additional funding to combat its growing illegal immigration problem.

More than 600 people have been caught trying to enter the country by sea since January.

Women and children

Australian Justice Minister Amanda Vanstone said the fishing boat appeared to have been specially fitted out to carry illegal immigrants.

She said seven women and 13 children were among the Iraqis found on board.

She added that the detainees were being looked after on Christmas Island by police at a sports pavilion.

Some of the Iraqis were suffering from dehydration and needed hospital treatment.

Immigration officials are travelling to the island to question the Iraqis and try to determine exactly which route they were taking to enter Australia.

Two Indonesian crewmen from the boat were arrested for people-smuggling, and are to appear in court in either Darwin or Perth on the Australian mainland.