Indonesian authorities have confirmed that one of the country's submarines has disappeared while participating in a training exercise in the waters between Java and Bali on Wednesday, April 21.
Indonesian defence ministry officials said in a statement that the Cakra-class diesel-electric submarine KRI Nanggala last made radio contact at 03:00 local time on Wednesday while conducting drills in the Bali Strait.
In their final radio transmission, the crew of the submarine, which was by then already submerged, asked for permission to dive even deeper.
Defence officials said that, after radio contact with Nanggala was lost, aerial surveillance patrols were conducted over the submarine's last reported position 96 kilometres off Bali.
An oil spill was spotted in the area by the crew of one of the patrolling aircraft at 07:00. Indonesian Navy spokesman First Admiral Julius Widjojono said the spill is "highly suspected" to have originated from Nanggala, which had a crew of 53 on board at the time of its disappearance.
Authorities believe the submarine went at least 100 metres lower than its rated crush depth of 500 metres.
Organisations from Australia, India, and Singapore have pledged to support the ongoing effort to locate the missing submarine, Indonesian Armed Forces chief Air Chief Marshal Hadi Tjahjanto told Reuters on Wednesday.