Search for missing Indonesian submarine enters second day as neighbours offer help

The Indonesian Navy said in a statement: "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 submarine was built to sustain pressure at a maximum depth of around 250 metres (820 feet), an official said.

The oil spill found on the surface could also mean there was damage to its fuel tank or could also be a signal from the crew, the navy said.

The military chief will hold a media briefing in Bali about the search on Thursday, a spokesman said.

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The 1,395-tonne KRI Nanggala-402 was built in Germany in 1977, according to the defence ministry, 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 bought from the Soviet Union to patrol the waters of its sprawling archipelago.

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

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