In a statement released Wednesday evening, the Indonesian Defense Ministry said the KRI Nanggala-402, a German-made submarine, lost contact during an exercise in the Bali Strait – a stretch of water between the islands of Java and Bali that connects on the Indian Ocean and the Bali Sea.
The submarine requested permission to dive or submerge at 3 a.m. local time (3 p.m. ET) before losing contact, he said. The statement added that an oil spill was seen at around 7 a.m. local time during aerial surveillance near the dive point.
Earlier on Wednesday, military chief Hadi Tjahjanto told Reuters they were “searching 53 people in the waters of Bali, 96 km from Bali.”
Singapore and Australia have offered to help.
The 1,395 ton KRI Nanggala-402 was built in 1977 by the German shipbuilder Howaldtswerke-Deutsche Werft (HDW) and joined the Indonesian Navy in 1981, according to the statement of the Ministry of Defense.
The submarine underwent a two-year refit in South Korea that was completed in 2012, according to the Indonesian Cabinet Secretariat’s website.
Indonesia had in the past purchased a fleet of 12 submarines from the Soviet Union to patrol the waters of the vast archipelago.
But now it has a fleet of just five, including two German-built Type 209 submarines and three newer South Korean ships.
Indonesia has tried to improve its defense capabilities, but some of its equipment still in use is obsolete and there have been fatal accidents in recent years, notably obsolete military transport aircraft.