Image caption Thousands of asylum seekers attempt to reach Australia by boat every year

A boat carrying about 150 suspected asylum seekers has capsized off Australia's Christmas Island, with four people confirmed dead.

Border authorities said two naval vessels had rescued 144 people from the water after the capsize on Tuesday.

The vessels were escorting the boat to a detention centre on Christmas Island but the ship overturned in rough seas.

Many asylum seekers try to reach the island, hoping then to move on to the Australian mainland.

Christmas Island, located about 1,600 miles (2,575km) north-west of the mainland, is the closest part of Australia to Indonesia - the key transit hub for people-smugglers.

Life rafts

"Overnight, our officers have rescued 144 people from the sea and recovered the bodies of four other people," Home Affairs Minister Jason Clare said.

It is a dreadful feeling in the stomach when we hear that a vessel has capsized David Johnston, Commander, Border Protection Comand

Australia's rescue co-ordination centre received a phone call from people on the vessel on early on Tuesday, after the boat's engine reportedly stopped, he said.

However, the "weather conditions and the high sides of the vessel" prevented rescue personnel from boarding the boat.

Navy vessel HMAS Albany reported that one of the two engines on the boat was not working and began escorting the boat, he said.

"At approximately 18:00, the vessel began to lean to one side and passengers began jumping into the water. At approximately 18:40, [HMAS] Albany reported that the vessel had rolled and capsized," Mr Clare said.

"A total of six life rafts were deployed" to rescue the passengers as well as an overhead Orion aircraft and small boats from the naval vessels, he said, thanking rescuers for their "tough, hard, difficult and dangerous work".

Customs said it had now suspended rescue efforts as there were no further signs of life.

Australia's irregular maritime arrivals 2010: 134 boats carrying 6,535 passengers

2011: 69 boats, carrying 4,565 passengers

2012: 278 boats carrying 17,202 passengers

2013 (figures up to 16 July): 218 boats carrying 15,182 passengers Figures from Australia's Department of Immigration; passenger numbers exclude crew

The boat overturned 70 nautical miles from Christmas Island.

Customs said in a statement: "HMAS Warramunga rescued 76 people from the water and HMAS Albany rescued 68 people from the water. Tragically, four deceased persons were recovered."

David Johnston, commander for Australia's Border Protection Command, said: "It is a dreadful feeling in the stomach when we hear that a vessel has capsized, or that it is in some difficulty."

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

Thousands of asylum seekers arrive in Australia by boat every year.

Several boats carrying migrants heading for Australia have disappeared in recent months.

In a separate incident on Saturday, 88 asylum seekers were rescued after their boat sank off the same island.

A baby boy died in the accident and eight people were missing and presumed dead. The boat, which set off from Indonesia, was reportedly carrying asylum seekers from Iran, Afghanistan and Sri Lanka.

New Australian Prime Minister Kevin Rudd is expected to announce new asylum policies in advance of Australia's general election, which must be held by November.

Refugee tribunals have been told to use new country assessments by the Department of Foreign Affairs and Trade when assessing asylum seeker claims, Australian broadcaster ABC reported.

Critics say this will lead to genuine asylum seekers being classed as economic migrants and being sent back to their original countries.