US joins hunt for lost Indonesian submarine as oxygen runs low

Indonesia is racing against time to find a missing submarine with 53 crew members before their air supply runs out, with the US and Australia joining the search for the vessel on Friday.

If the diesel-powered KRI Nanggala-402 suffered an electrical failure, its oxygen could be depleted by the early hours of Saturday, according to Admiral Yudo Margono, the Indonesian navy chief of staff.

Authorities have yet to make contact with the submarine, which went missing in deep water near Bali during a torpedo-firing exercise on Wednesday.

Yudo on Thursday evening said the search teams had found an unidentified object with “strong magnetic force” at a depth of between 50 and 100 metres, which authorities hoped might be the missing vessel.

An Indonesian ship with sensors that could identify the object was due to arrive at the search site later on Friday.

Indonesia’s navy operates five submarines, two of which, like the KRI Nanggala-402, were built in Germany and the remainder in South Korea.

Patrolling the country’s vast maritime borders and myriad islands is a challenge for Jakarta, which has also been involved in disputes with Beijing over fishing rights in the South China Sea.

The US on Friday sent a maritime patrol plane from the Philippines to help with the search, according to Indonesia’s armed forces.

The Pentagon said it was “sending airborne assets . . . at the invitation of the Indonesian government”.

Lloyd Austin, US secretary of defence, and his Indonesian counterpart, Prabowo Subianto, would “discuss how else the United States can be of assistance”, the Pentagon added. 

Australia on Friday also sent two warships. “These two Australian ships will help expand the search area and extend the duration of [the] search effort,” said Rear Admiral Mark Hammond, commander of the Australian fleet.

Washington and Canberra’s moves come after Malaysia, Singapore and India on Thursday sent specialised rescue ships to help search for the submarine, which was built four decades ago and completed an overhaul in South Korea in 2012.

Jakarta’s search squad involving ships and a helicopter initially found oil spills and detected the smell of diesel fuel in several locations, but the armed forces said it could not “be concluded that it [was] submarine fuel”.

The Indonesian navy on Wednesday said a blackout might have occurred during “static diving”, making the submarine lose control and fall to a potential depth of between 600 and 700 metres.

This was more than twice the maximum depth at which experts say submarines can navigate safely.

Additional reporting by Katrina Manson