SYDNEY - Refugee advocates Monday called for an inquiry into the way Australia monitors boats carrying asylum-seekers as five people were missing presumed dead after leaving their stricken vessel for help.

Authorities had been tracking the boat off Australia's northwest coast for days and started a search after it failed to arrive at the Cocos Islands as expected on Wednesday. Fifty-nine survivors were rescued Saturday.

"I think there's a real question mark over the response of the Australian authorities," Ian Rintoul from the Refugee Action Coalition told AFP.

"They had been tracking the boat for a number of days before it got into distress. They were aware it was in distress.

"Whether it's complacency or negligence I don't know. We need an inquiry."

Australian Customs received a distress call from the boat on April 30 which said it had run out of fuel, food and water as it headed towards the Cocos Islands, an Australian territory in the Indian Ocean.

But a passing merchant ship, which was asked to provide assistance, later reported the boat was seaworthy and those on board in good health.

When the boat failed to arrive on Wednesday, a search was launched and a surveillance aircraft saw the vessel about 160 nautical miles offshore. Four ships in the area were asked to respond.

Sailors on a Russian vessel that met the boat on Friday were told that five people had set off in a makeshift raft cobbled together from lifejackets and tyre tubes, but had not returned.

"If reports about five missing passengers are correct, this is a tragic and unnecessary loss of life, and highlights that these types of voyages are extremely dangerous," Home Affairs Minister Brendan O'Connor said Sunday.

"Unfortunately, loss of life at sea can occur when people are persuaded to embark on these poorly maintained vessels over such a great distance."

O'Connor said a search for the five had been called off because there was no hope now of finding them alive, but that 59 other asylum-seekers were taken to the Cocos Islands by the Russian ship.

The Australian Greens party also called for an inquiry into the tragedy.

"Obviously something is not working right when we know a boat was there and two weeks later five people are dead," Senator Sarah Hanson-Young said.

Rickety boats carrying asylum-seekers from trouble-spots such as Sri Lanka and Afghanistan have been arriving in Australia every few days, putting pressure both on facilities and Prime Minister Kevin Rudd.