CANBERRA - The Australian Government is defending itself against claims of callous indifference to the deaths of 163 illegal migrants drowned when their two boats foundered in cyclone-driven seas.

Although aircraft were yesterday flown over the area to check for survivors, no full-scale search was launched when news of the sinkings reached Canberra.

Anger is also mounting against the people-traffickers who put the boats to sea despite the approach of Tropical Cyclone Sam as they left Indonesia for Ashmore Reef, the barren outcrop off the coast of Western Australia where many boatpeople are landed.

Reports from Indonesia said the man who put the boats to sea had fled to escape the wrath of relatives of the dead. The drownings followed the deaths of up to 350 boatpeople this year and an extensive drive by Australia to both discourage migrants from making what is always a dangerous journey and to crack down on rapidly growing people-smuggling rackets.

The pressure of a rising wave of illegal migrants has forced Canberra to develop new holding centres amid outcries over the conditions in which many are held and the rigorous detention policies that put them there.

The latest sinkings occurred somewhere between Indonesia's eastern islands and Australia. Two boats, one with 80 people, the other with 87, left last week.

A Japanese tanker rescued four survivors.

Although the area is patrolled regularly by Government aircraft, Canberra did not order a serious search, apparently because of doubts over responsibility and the lack of a location beacon.

The decision not to search for survivors contrasted with the effort made to rescue lone British yachtsman Tony Bullimore, and the implication that the victims had only themselves to blame.

"Whatever we might think about them they were coming to this country full of hope," said Greens Senator Bob Brown. "We should be showing compassion."

But Immigration Minister Philip Ruddock said search teams needed to know where to look in what was a very large tract of ocean.

"These boats that people leave in don't carry the sort of devices that we see on yachts," he told the Nine Network. "It's like looking for a needle in a haystack."