Up to 60 asylum seekers are believed to be missing or dead after another boat sank off Indonesia.

A major rescue operation is reportedly underway to find survivors. It is being coordinated by Indonesian authorities.

It is believed the vessel left a fishing village on the south coast of the Indonesian island of Java early on Tuesday morning but didn't get far before running into trouble, News Australia has reported.

Local fishermen rescued about 120 people overnight but another 60, including children, are believed to be missing or dead.