Rescuers in Indonesia have plucked to safety 13 more people including eight foreigners, two days after their tourist boat sank as it travelled between islands in the east of the archipelago, a search and rescue official has said.

"They were all found together, some in a lifeboat and some floating with their life jackets on around 60 miles (100 kilometres) off Sape," on the east of Sumbawa island, said search and rescue official Budiawan, who like many Indonesians goes by one name. 

He could not immediately give details of their nationalities. A total of 18 foreigners and five Indonesians have now been rescued following the weekend sinking, and two foreigners remain missing.

The tourist vessel went down on Saturday after being caught up in a storm en route from Lombok island to Komodo island.

Bertrand Homassel, a French survivor, said the boat started sinking slowly after its hull was damaged in a storm on Friday night, and he and several others had to swim a long distance to a volcanic island to save themselves.

"Six people were in the lifeboat. The others climbed onto the roof of the boat, which had not completely sunk", he said, speaking from a hotel in Bima on Sumbawa island, where the survivors were taken after being rescued.

"We waited until midday on Saturday. We were five kilometres from the coast -- there were many big waves separating us from the coast.

"People started to panic... Everyone took the decision to swim to the closest island where there was an erupting volcano."

He said that they swam for six hours and arrived on the island, Sangeang, as the sun was setting. They spent Saturday night there, surviving by drinking their own urine and eating leaves.

On Sunday, they attracted the attention of a passing boat by waving their life jackets, and were rescued and taken to Bima, he said.

"I was really very lucky," Homassel added.

Indonesia relies heavily on boats to connect its more than 17,000 islands, but has a poor maritime safety record.

Two vessels sank last month in different parts of the archipelago as millions travelled for the Muslim Eid holiday, leaving at least 36 people dead.

Source: AFP