JAKARTA — At least four people have died and dozens are missing after a ferry sank off Indonesia's tourist island of Bali, rescuers said.

The boat was carrying 53 passengers and 12 crew members when it sank at 23:20 local time (15:35 GMT) on Wednesday while on its way to Bali from Banyuwangi on the eastern coast of Java island, the Surabaya office of the National Search and Rescue Agency said.

Thirty-one survivors have been rescued, the agency says, as the search continues.

Authorities are investigating the cause of the sinking. The ferry operator had reported engine trouble shortly before it sank, while an official said the cause was "bad weather", according to local media.

Many of the survivors are residents of the coastal town of Banyuwangi while others came from more inland areas of Java, according to a list released by authorities.

President Prabowo Subianto has ordered an immediate emergency response from Saudi Arabia, where he is on an official visit.

The vessel's route - one of Indonesia's busiest - is often used by locals going between the islands of Java and Bali.

Photos published by Antara news agency showed ambulances on standby and residents waiting for updates by the roadside.

Marine accidents are frequent in Indonesia, a sprawling archipelago of around 17,000 islands, where uneven enforcement of safety regulations is a longstanding concern.

In March, an Australian woman died after a boat with 16 people on board capsized off Bali. — BBC