The International Organization for Migration says more than 350 people drowned off the coast of Indonesia when their boat sank. The agency's headquarters in Geneva that 44 survivors were rescued over the weekend.
The International Organization for Migration says most of the passengers on board the vessel were Iraqis, but included Iranians, Afghans, Palestinians and Algerians.
The destination of the boat is not known, but thousands of illegal migrants pass through southeast Asian seas in search of refuge in richer countries, such as Australia.
The IOM says the boat had set sail from the Indonesian island of Java on Thursday. The following day, the boat's captain reported that his engines had stopped and that the boat was taking in water.
An agency spokesman says the survivors were picked up on Saturday, after spending hours in the Java sea, and were cared for in the Indonesian port of Bogor.
The agency has sent a medical team to assist the migrants.