Indonesia blew up and sank three empty Vietnamese boats Friday, the navy said, as the world's biggest archipelago nation pushes to stop foreigners from illegally fishing in its waters.
It was the strongest measure yet taken in the campaign launched by new President Joko Widodo, known as Jokowi, who is seeking to stop a practice he says costs Southeast Asia's biggest economy billions of dollars in lost revenues.
The navy, working with other government agencies, sank the three boats in the remote Anambas Islands, which lie between Malaysia and the Indonesian part of Borneo island, navy spokesman Manahan Simorangkir told AFP.
"The message we want to convey is no foreigners should steal from Indonesian waters," he said, adding Indonesians should be able to "benefit from their own waters".
The Jakarta Post newspaper reported that explosives were attached to the boats before two government vessels fired on them from a distance.
Thirty-three people had been detained and three tonnes of fish seized from the ships, which were caught last month, it said.
Television pictures showed thick smoke billowing from one of the boats as it sank.
As well as costing the economy billions, authorities say foreigners illegally fishing in Indonesia is partly responsible for massive damage to the environment due to the widespread use of explosives and cyanide.
Widodo hopes that increased revenues from fishing can help boost economic growth, which has sunk to a five-year low.