Indonesia's navy searching for 53 people on board a missing submarine

HONG KONG -- An Indonesian submarine with 53 on board is feared missing after the country's military lost contact with it Wednesday during an early morning torpedo training exercise in the waters north of Bali.

The 42-year old German-made submarine, KRI Nanggala-402, is part of the Indonesian Navy's 2nd Fleet and was taking in naval drills that were supposed to culminate on Thursday.

Indonesia's military chief Marshal Hadi told the local outlets that he has asked Singapore and Australia for assistance, with whom Jakarta has signed submarine rescue agreements with. They are expected to join several of the Indonesian warship already dispatched to the area to aid in the rescue efforts.

Tjahjanto is expected to travel to Bali Thursday morning, where he was originally scheduled to oversee the final exercises but now he will give an update on the search for the KRI Nanggala.

Tjahjanto told local outlet Kompas that the submarine disappeared in waters about 60 miles the north of Bali Island around 3 a.m. local time, but told Reuters they lost contact around 4:30 a.m.

"Just when the dive permit was given, after being given the clearance, contact was immediately lost," Hadi told Kompas.

A source in the Indonesian Navy told ABC News that Nanggala-402 was last in contact around 3 a.m. when it was given clearance to dive. The Navy was expecting the crew to check in before it was supposed to resurface around 6 a.m. local for a flotilla exercise.

According to the source, the surface crew became increasingly worried with each passing hour with contact until, according to Janes, a defense news outlet, the Indonesian armed forces sent out a distress call to the International Submarine Escape and Rescue Liaison Office at about 9:37 a.m. local time to report the submarine as missing with the presumption that it has sunk.

According to Reuters, the 1,395-tonne vessel was built in 1978 and underwent a two-year retrofit in South Korea in 2012.