EAST JAVA: Rescuers searched into the night Tuesday for seven missing people after a ferry sank with more than 50 people onboard in rough seas near Indonesia's resort island of Bali, killing at least six people, officials said.

The ferry, the KMP Yunice, sank about half an hour after leaving East Java's Ketapang port, authorities said.

It was bound for Bali's Gilimanuk port, a 50-kilometre (30-mile trip), with 41 passengers and 12 crew members.

Officials said 40 people, many unconscious after drifting in choppy waters for hours, were rescued and at least six bodies were recovered.

"It happened very suddenly" said Hayati Ayu, a survivor. "The ship overturned and began to sink, and I was helped and lifted from the water."

Rescuers were battling waves up to four metres (13 feet) high in darkness to search for the missing people.

Ferry tragedies are common in Indonesia, an archipelago of more than 17-thousand islands, with weak enforcement of safety regulations often to blame.

In 2018, an overcrowded ferry with about 200 people on board sank in a deep volcanic crater lake in North Sumatra province, killing 167 people.

In one of the country's worst recorded disasters, an overcrowded passenger ship sank in February 1999 with 332 people aboard. There were only 20 survivors.