Indonesia's National Search and Rescue Agency (Basarnas) received an alert from the Australian Maritime Safety Authority (AMSA) at around 1:30 am that a boat was in distress between Java and Sumatra.
"We received a fax from Australia in the early morning saying there was boat sinking in the Sunda Strait," Basarnas officer on duty Yopi Haryadi told AFP.
"We sent two 36-metre police rescue boats at around five in the morning, and two helicopters at around 9:30, but so far there is no sign of the vessel or any survivors."
Haryadi said the boat sent a distress signal 220 nautical miles from the Australian Indian Ocean territory of Christmas Island carrying around 150 people, according to information received from AMSA.
Canberra is facing a steady influx of asylum-seekers arriving in Australia by boat, many of whom use Indonesia as a transit hub, boarding leaky wooden vessels after fleeing their home countries.
Australian authorities this month said 300 boatpeople had died en route to the country this year, with boats being intercepted by the Australian navy almost on a daily basis.
Two weeks ago, Canberra announced its intention to transfer asylum-seekers to Nauru and Papua New Guinea in the Pacific as part of a tough new policy to deter them from making the dangerous sea voyage.
But they keep coming, with more than 1,000 boatpeople arriving since the policy was adopted.
The new policy represents a return to the harsh era of the previous conservative government that sent asylum-seekers to Nauru and PNG but which the centre-left Labor rolled back soon after taking office in late 2007.
