Indonesian rescuers searching for a submarine that went missing with 53 people on board found an oil spill on Wednesday near where the vessel dived, authorities said.
The 44-year-old submarine, KRI Nanggala-402, was conducting a torpedo drill 95 kilometres north of Bali but failed to relay the results as expected, a navy spokesman said.
An aerial search found the oil spill and two navy vessels with sonar have been sent to assist in the search, the Defence Ministry said.
It said requests for assistance had been made and Australia, Singapore and India had responded.
Contact with the vessel was lost at 4.30am on Wednesday, military chief Hadi Tjahjanto told Reuters.
"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 to 700 metres," the Indonesian Navy said.
The submarine was built to sustain pressure at a maximum depth of about 250 metres, an official said.
The oil spill found on the surface could also mean there was damage to its fuel tank, or it could be a distress signal from the crew, the navy said.
The military chief will hold a briefing to share further information about the search on Thursday from Bali, a spokesman said.
