Australia has been asked to help with the search for an Indonesian military submarine that has gone missing north of Bali with 53 people on board.

The Indonesian Defense Ministry said Australia, Singapore and India had all responded to its requests for assistance with the hunt for the 44-year old KRI Nanggala-402 sub.

Both Australia and Singapore have submarine rescue vessels. Australian officials have not yet confirmed what help they may provide.

Oil spill could be an SOS signal

Reuters reports an oil spill has been spotted near where the German-made submarine went missing while conducting a torpedo drill. It was rehearsing for a missile-firing exercise that was to take place on Thursday.

The oil seen by aerial searchers could indicate there was damage to the submarine’s fuel tank, or it could have been deliberately released as a sign by the crew, officials said.

“We are still searching in the waters off Bali, 96 km from Bali, (for) 53 people,” military chief Hadi Tjahjanto told Reuters in a text message. He said contact with the vessel was lost at 4.30am on Wednesday (local time).

The submarine was built to sustain pressure at a maximum depth of around 250 metres.

“It is possible that during static diving, a blackout occurred so control was lost and emergency procedures cannot be carried out and the ship falls to a depth of 600-700 metres,” the Indonesian Navy said in a statement.

An Indonesian search and rescue vessel prepares to leave Bali. Photo: AAP

Submarine is a 1970s vintage

The 1,395-tonne KRI Nanggala-402 was built in Germany in 1977, and joined the Indonesian fleet in 1981. It underwent a two-year refit in South Korea that was completed in 2012.

Indonesia in the past operated a fleet of 12 submarines purchased from the Soviet Union but now only has a fleet of five – two German-built Type 209 submarines and three newer South Korean vessels.

Indonesian navy submarine which has disappeared with 53 people on board, in waters north of Bali. (photos from Indonesian navy) pic.twitter.com/T8CiVuZ6lG

— Anne Barker (@AnneABarker) April 21, 2021

Indonesia has been seeking to upgrade its defence capabilities but some of its equipment still in service is old and there have been deadly accidents involving, in particular, ageing military transport planes in recent years.

In 2015, an Indonesian military transport plane crashed into a residential area two minutes after takeoff, killing more than 100 people. In 2016, an Indonesian air force transport plane crashed into a mountain, killing all 13 people board, during a training exercise in the remote region of Papua.

-with agencies