Two asylum seekers drowned and two more were seriously injured when their boat was hit by two freak waves minutes after being boarded by two border protection officials within 15 nautical miles of Christmas Island on Monday.
The deaths of a young boy and a woman in her 30s, believed to be from Afghanistan, have led to calls for a review of protocols for intercepting asylum seekers' boats.
The tragedy – the first off Christmas Island since the Gillard government accepted all the recommendations of its expert panel on asylum seekers – prompted warnings of more deaths at sea from former immigration minister Gerry Hand.
Prime Minister Gillard described the tragedy as "dreadful", saying too many people had lost their lives getting on these "very dangerous" boats. "So my message is a very clear one," she said. "Do not pay a people smuggler. Do not get on a boat."
Home Affairs Minister Jason Clare said the boat was one of several launched by people smugglers during a break from monsoonal weather that had "provided an opportunity for the people who peddle in this evil trade".
Mr Clare said that while the boat had been spotted at 4pm (Melbourne time) on Sunday afternoon, it had not appeared to be in distress before it was intercepted, around 40 minutes after daylight on Monday, and boarded.
Border protection commander Rear Admiral David Johnston said his officers had followed established protocols in waiting for first light in the absence of signals of distress to board the boat, a converted Indonesian fishing vessel.
He said conditions at the time were "certainly within our ability to manage safely" before the two large waves rocked the boat.
Greens senator Sarah Hanson-Young said the protocols should be reviewed with a view to boarding vessels earlier – a call supported by George Newhouse, a lawyer representing survivors of the 2010 tragedy off Christmas Island. Senator Hanson-Young said it was clear that the "punitive" measures adopted on August 13 last year, including sending asylum seekers to Nauru and Papua New Guinea's Manus Island, were not deterring arrivals.
The injured asylum seekers were a young boy and a pregnant woman in her 20s. They were among 93 people, including 17 "juveniles", rescued from the boat, the sixth to arrive off Christmas Island in three days.
Rear Admiral Johnston said the nationalities of those on board was unknown, however, it appeared they were from Afghanistan and Middle Eastern countries. Three Indonesians have also been identified.
Mr Clare said that, with the monsoon season to continue until end of April, there was "potential for conditions to get much more dangerous in weeks ahead".
Opposition immigration spokesman, Scott Morrison said news of the tragedy sadly came as no surprise. "Every vessel that seeks to come to Australia in this way puts everyone's life at risk, including those called upon to conduct the rescue," he said.
"Another two souls have been lost at sea as the chaos, cost and tragedy continues on our borders. They join more than a thousand who are believed to have perished as a result of trying to make this dangerous journey."
Mr Hand predicted more tragedies until a regional agreement was reached. "I hate to say it, but I've no doubt there will be more (deaths) as the boats intensify after the monsoon season," Mr Hand told Sky News. "The only solution here is a regional approach and that has to be an objective."
The Gillard government recently appointed the head of its expert panel, former defence chief Angus Houston, as a special envoy to build support for a regional approach.
Mr Newhouse, the head of of the Shine Lawyers Social Justice team, said it was vital that appropriate care and counselling was provided to the survivors, insisting this was not the case in the 2010 tragedy, known as the SIEV 221 disaster, that claimed around 50 lives.
"It is too early to determine fault or blame, but the Government appears not to have learned the lessons of the SIEV 221 disaster. It is arguable that the Commonwealth owed a duty of care to take reasonable steps to detect, intercept and detain the asylum seekers before the tragedy," he said.