A wooden ship believed to be carrying more than 380 migrants, many of them from the Middle East, sank off Indonesia's main island of Java, local media have reported.

Police blamed the accident on overloading, telling the official news agency Antara on Saturday that the vessel appeared to have been carrying more than twice its capacity.

So far only 76 people have been rescued, said Sahrul Arifin, the head of emergency and logistics at the East Java Disaster Mitigation Centre.

He said strong waves wrecked the wooden boat about 90km out to sea. "Our search and rescue team have begun sweeping the water around where the accident took place but we are now sending body bags to that area."

One of the survivors, Esmat Adine, told Antara the vessel began rocking from side to side, which triggered widespread panic.

The passengers were very tightly packed, and therefore had nowhere to go, said the 24-year-old Afghan migrant.

"That made the boat even more unstable and eventually it sank," he added.

Adine said that he and others survived by clinging onto parts of the broken vessel until they were picked up by local fishermen.

He estimated that more than 40 children were on the ship. It was not immediately clear if any were rescued.

Indonesia, a sprawling archipelagic nation of 240 million people, has more than 18,000 islands and thousands of kilometres of unpatrolled coastline, making it a key transit point for smuggling migrants.

Those on board on Saturday - apparently heading to Australia - were from Afghanistan, Turkey, Iran, and Saudi Arabia.

The private television station Metro TV reported that 33 people had been found alive and that perhaps 215 others were still missing.

Last month, a ship carrying about 70 asylum seekers from Afghanistan, Iran and Pakistan capsized off the southern coast of Central Java; at least eight people died.