Indonesia's navy has lost contact with a submarine carrying 53 sailors that was preparing for a weapons training exercise in waters north of Bali, a military spokesman Wednesday.
The German-built KRI Nanggala-402, which went into service in the early 1980s, failed to relay results of the exercise as expected, Julius Widjojono said, according to Reuters.
Indonesia's military chief, Hadi Tjahjanto, told Reuters that officials are seeking help from Australia and Singapore in the search for possible survivors.
"We are still searching in the waters of Bali, 60 miles from Bali, (for) 53 people," he told the news agency in a text message.
Local media reported that the navy believes the sub went down in an area where the seafloor features a 2,300-foot-deep trough.
The German-built submarine, which has been in service since the early 1980s, was rehearsing for a missile-firing exercise that was to take place on Thursday and be attended by Tjahjanto and other military leaders.
Indonesia currently has a fleet of five submarines and plans to operate at least eight by 2024.
Contact with the vessel was lost at 4:30 a.m. on Wednesday local time (5:30 p.m. Tuesday ET), he said.
Tjahjanto told Indonesia's Kompas media that contact was lost after the submarine had been given permission to dive.
The Indonesian military sent out a distress call to the International Submarine Escape and Rescue Liaison Office (ISMERLO) at about 9:37 a.m. local time to report the boat missing and presumed sunk, according to Jane's.
Representatives of the defense departments of Australia and Singapore did not immediately respond to requests for comment, Reuters said.
The Indonesian navy has sent several vessels to the search area, Jane's reported.
Indonesia operates a fleet of five military submarines, including two built in Germany and three newer South Korean-built boats, according to Reuters.
This is a developing story. Some facts reported by the media may later turn out to be wrong. We will focus on reports from police officials and other authorities, credible news outlets and reporters who are at the scene, and we will update as the situation develops.