Four soldiers were killed and eight were wounded after a Chinese-made cannon malfunctioned and fired off shots randomly during military exercises in Tanjung Datuk, Natuna, Riau Islands province, on Wednesday (May 17).

Army spokesman Alfret Denny Tuejeh said eight other soldiers were wounded in the accident Wednesday in the Tanjung Datuk region of Riau Islands province.

He said the malfunction of the twin-barreled gun caused it to fire in unexpected directions and hit the soldiers, who are members of the Quick Response Team of the Army’s Air Defense Artillery Unit. Four of the wounded are in serious condition.

Tuejeh said an investigation is underway to find out why the weaponry, purchased from China in 2003, malfunctioned.

Indonesia has boosted its military presence in the Natuna islands, which are in the southernmost reaches of the South China Sea, in response to Beijing’s assertive posture in the region.