Home Affairs minister Jason Clare has told the media of the size of the rescue operation underway north of Christmas Island, where a suspected asylum vessel has capsized.
He said rescucers have picked up 110 survivors from an asylum seeker boat that capsized on its way to Australia from Sri Lanka with up around 200 people on board.
Mr Clare said that early reporting suggested that all the passengers were male. One thirteen -year-old boy had been rescued, while the bodies of three adult men had been recovered.
The Australian Maritime Safety Authority, which is working with Indonesia's search and rescue authority BASARNAS, said search and rescue operations have continued throughout the night.
Two Australian navy patrol boats, HMAS Larrakia and HMAS Wollongong, are already involved.
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Three aircraft will provide support - an AMSA plane, an airforce craft and also a customs plane
Mr Clare also said that four merchant vessels are on their way to assist in what the minister referred to as a 'critical window.' It is thought that with a water temperature of 29c, there is a good chance of more survivors.
The 110 survivors have been taken to Christmas Island, which quickly activated its emergency management plan and prepared its hospital and medical staff.
Earlier, Prime Minister Julia Gillard spoke with Indonesian President Susilo Bambang Yudhoyono in Rio de Janeiro, where they are attending a UN environment conference.
"At this stage details are sketchy but what is apparent is there has been a large loss of life at sea," Ms Gillard told reporters.
"This is a very distressing and tragic incident."
Home Affairs Minister Jason Clare will make a statement on Friday morning.
Acting Prime Minister Wayne Swan is in charge of security arrangements.
The disaster began to unfold after 3pm (AEST) on Thursday, when an Australian Customs and Border Protection surveillance plane spotted a vessel "in distress" 200km north of Christmas Island.
The observers immediately contacted Indonesian authorities, who are leading the rescue effort alongside the Australian navy, defence and customs.
In December 2010, more than 50 asylum seekers died when a boat known as SIEV 221 crashed against rocks off Christmas Island.
The youngest was just three months old.
The disaster was the largest loss of life in Australian waters in peacetime in 115 years.
Last December, as many as 200 people drowned when an overloaded boat sank off the coast of East Java on its way to Australia.
Just 49 people survived that tragedy, which occurred in rough monsoonal seas on December 17.
So far this year, 57 boats carrying a total of 4006 passengers and 82 crew have arrived in Australia.
For the month of June, there have been 18 boats carrying more than 1100 people.
The latest arrived arrived overnight on Thursday and had 117 people on board.
