SYDNEY: A boat carrying about 150 asylum seekers capsized in monstrous Indian Ocean waves, triggering a frantic rescue effort by Australian crews who saved nearly every passenger from the churning water, officials said Wednesday.

Four people died after the boat rolled over Tuesday in choppy seas 125 kilometres north of Christmas Island, Home Affairs Minister Jason Clare told reporters.

The Australian island is 500 kilometres south of Jakarta, Indonesia.

The survivors, from Afghanistan, Pakistan, Iran and Iraq, were taken to Christmas Island, along with three Indonesian crew members.

A navy ship was sent to assist the vessel after it was spotted by an aircraft patrol on Monday, Clare said.

When the navy ship arrived, the boat appeared to be in good condition. By Tuesday, however, several on board had called maritime authorities asking for help, saying the engines had stopped working.

A second navy ship was sent to the scene and rescuers attempted to board the boat. But towering, four-metre waves coupled with the vessel's high sides made climbing on board impossible, said David Johnston, Commander of Australia's Border Protection Command.

Rescuers decided the safest option would be to escort the boat to Christmas Island, where Australia operates a detention camp for asylum seekers.

Several hours into the journey, however, the boat started leaning and some passengers began jumping into the water. Shortly after, the boat rolled and capsized, Clare said. Officials don't know what caused the boat to flip.

Rescuers dropped life rafts into the water and hopped into small boats to reach the scores of men, women and children struggling against the choppy waves.

Officials managed to pluck 144 people to safety, and recovered the bodies of two women and two men before calling off the search Tuesday night.

There were around 19 infants and children on board, Johnston said.

''It is a dreadful feeling in the stomach when we hear that a vessel has capsized, or that it is in some difficulty,'' Johnston said.

''Recovering 144 people in the conditions they had yesterday was extraordinary work.''

Customs officials estimated the boat had 150 passengers and said they were interviewing survivors to determine the exact number. They aren't searching for more people. Christmas Island is a popular destination for asylum seekers who crowd into rickety boats at Indonesian ports and pay people smugglers to ferry them to Australian shores.

Hundreds have died while attempting the journey in recent years.

Last week, another boat carrying asylum seekers sank off Christmas Island. Officials recovered the body of a baby boy and were unable to find eight passengers who vanished in the water.