Denpasar (Indonesia) (AFP) – At least four people were dead and dozens unaccounted for Thursday after a ferry sank on its way to the resort island of Bali, according to local authorities who said 23 survivors had been plucked from the water so far.

Rescuers were racing to find 38 missing people in rough seas after the vessel carrying 65 passengers sank before midnight on Wednesday as it sailed to the popular holiday destination from Indonesia's main island Java.

"23 rescued, 4 dead," Rama Samtama Putra, police chief of Banyuwangi in East Java, where the boat departed, told AFP.

President Prabowo Subianto, who was on a trip to Saudi Arabia, ordered an immediate emergency response, cabinet secretary Teddy Indra Wijaya said in a statement Thursday, adding the cause of the accident was "bad weather".

Java-based Surabaya search and rescue agency head Nanang Sigit confirmed the same figures in a statement, and said efforts to reach the boat were initially hampered by adverse weather conditions that have since cleared up.

Waves as high as 2.5 metres (8 feet) with "strong winds and strong currents" had affected the rescue operation, he said.

The agency had earlier said 61 people were missing and four rescued, without giving a cause for the boat's sinking.

"KMP Tunu Pratama Jaya... sank about 25 minutes after weighing anchor," it said.

"The ferry's manifest data totalled 53 passengers and 12 passenger crews."

A rescue team of at least 54 personnel including from the navy and police were dispatched along with inflatable rescue boats, while a bigger vessel was later sent from Surabaya city to assist the search efforts.

The ferry crossing from Ketapang port in Java's Banyuwangi regency to Bali's Gilimanuk port -- one of the busiest in Indonesia -- is around 5 kilometres (3 miles) as the crow flies and takes around one hour.

It is often used by people crossing between the islands by car.

Four of the known survivors saved themselves by using the ferry's lifeboat and were found in the water early Thursday, the rescue agency said.

It said the ferry was also transporting 22 vehicles, including 14 trucks.

It was unclear if any foreigners were onboard when the ferry sank.

Rescuers said they were still assessing if there were more people onboard than the ferry's manifest showed.

It is common in Indonesia for the actual number of passengers on a boat to differ from the manifest.

Marine accidents are a regular occurrence in Indonesia, a Southeast Asian archipelago of around 17,000 islands, in part due to lax safety standards and sometimes due to bad weather.

In March, a boat carrying 16 people capsized in rough waters off Bali, killing an Australian woman and injuring at least one other person.

A ferry carrying more than 800 people ran aground in shallow waters off East Nusa Tenggara province in 2022 and remained stuck for two days before being dislodged with no one hurt.

And in 2018, more than 150 people drowned when a ferry sank in one of the world's deepest lakes on Sumatra island.