"The vessels were approached by the Oceanic Viking and were instructed to leave the Convention for the Conservation of Antarctic Marine Living Resources Commission waters," Macdonald said in a statement on Friday.

"But because the flag states of these vessels are not members of the commission, international law does not allow any additional action to be taken. Evidence of the vessels' fishing was being gathered and will be passed to the commission."

Illegal fishing for the rare Patagonian toothfish has been on the rise in recent years with demand for its white, flaky flesh rising in Asia and the United States. One shipload of the fish, dubbed "white gold", is worth up to A$5 million ($3.9 million).

Macdonald said the six vessels were fishing in an area where the 24-nation commission had stopped fishing on Feb. 14 because the annual quota for Patagonian toothfish, also known as Chilean Sea Bass, had been reached.

Marine conservationists have warned the toothfish could become commercially extinct by 2007 because illegal fishing above the quotas was already depleting dwindling stocks.

"I am highly critical of the international community for not addressing the problem that has been clearly exposed again this week," Macdonald said, adding that Australia made representations to Togo but to no avail.

The Oceanic Viking patrols Australia's Exclusive Economic Zone around Heard and McDonald islands and the edge of the Antarctic ice shelf, more than 4,000 km (2,500 miles) southwest of the West Australia coast.

In August 2003 Australian authorities spotted the Uruguayan-flagged Viarsa illegally fishing in the area and spent A$5 million chasing it though stormy 10 metre (33 feet) seas and dodging icebergs before catching it off South Africa.