JAKARTA • Indonesia's navy is searching for a submarine with 53 people on board that went missing yesterday and is seeking help from neighbouring Australia and Singapore in the hunt, the Indonesian military chief told Reuters.

The German-made submarine, KRI Nanggala-402, was conducting a torpedo drill in waters north of the island of Bali but failed to relay the results as expected, said a navy spokesman.

"We are still searching in the waters of Bali, 60 miles (96km) from Bali, (for) 53 people," military chief Hadi Tjahjanto said in a text message.

He confirmed that assistance in the search for the submarine and its missing crew members had been sought from Australia and Singapore.

He said contact with the vessel was lost at 4.30am yesterday.

An aerial search found an oil spill near the submarine's dive location and two navy vessels with sonar capability have been deployed to assist the hunt, Indonesia's Defence Ministry said.

The 1,395-tonne KRI Nanggala-402 was built in Germany in 1978, according to the Indonesian Cabinet secretariat's website, and 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 to patrol the waters of its sprawling archipelago.

But now it has a fleet of only five, comprising two German-built Type 209 submarines and three newer South Korean vessels.

Meanwhile, a statement by the Indonesian Defence Ministry, which is monitoring the search for the missing submarine, said aerial surveillance by a helicopter at 7am (Jakarta time) had found an oil spill around the initial dive site.

The missing boat "had asked for permission to dive at 3am (Jakarta time)", said the statement.

"After being granted a dive permit according to the procedure, the boat lost contact and could not be contacted," it added.

The ministry said: "Several countries have responded and are ready to provide assistance, including the Singapore Navy, the Australian Navy and the Indian Navy."

Indonesia has been seeking to modernise its defence capabilities, but some of its equipment still in service are old and there have been deadly accidents in recent years.

In 2016, an Indonesian air force transport plane crashed into a mountain, killing all 13 people on board, during a training exercise in the remote region of Papua.

In 2015, an Indonesian military transport plane crashed into a northern residential area two minutes after take-off, killing more than 100 people.

REUTERS, AGENCE FRANCE-PRESSE