Four Indonesian soldiers have been killed and eight others injured by artillery fire in an accident during training on a South China Sea island, the army said Thursday.
It took place Wednesday when an artillery cannon malfunctioned during the exercise involving an army reserve battalion on Tanjung Datuk Natuna, on the northwestern fringe of the vast Indonesian archipelago.
"The cannon became uncontrollable and hit soldiers in the vicinity," army spokesman Alfret Denny Tuejeh told AFP.
Of the eight hurt, four suffered serious injuries, he said.
The cannon, purchased in 2003, was used a day before without any problem, he added. The military have begun an investigation to find out what caused the incident.
The island is part of the small Natuna archipelago, remote Indonesian islands in the South China Sea, home to rich fishing grounds and abundant oil reserves.
There have been repeated clashes between Chinese and Indonesian vessels around the islands in recent times, prompting Indonesia to bolster its defences in the area.
Indonesia maintains it has no maritime disputes with China in the South China Sea, unlike other Asian nations, and does not contest ownership of reefs or islets there.
But Beijing's expansive claims in the sea overlap Indonesia's exclusive economic zone -- waters where a state has the right to exploit resources -- around the Natunas.
China has defended its incursions into Indonesian waters around the islands, saying its trawlers are operating in "traditional Chinese fishing grounds".But Jakarta disputes this.