Debris from missing Indonesian submarine kills hopes for survivors

A missing Indonesian submarine with 53 crew on board is believed to have sunk and cracked open after debris was found in the area of its last dive, the country's naval and military chiefs said on Saturday, ending hopes of finding survivors.

Contact with the KRI Nanggala-402 was lost on Wednesday as it prepared to conduct a torpedo drill in the sea off the island of Bali. A search operation involving several countries has been unable to locate the vessel.

"Over the past few days we've recovered debris and items from the last location that the submarine was diving," Navy Chief of Staff Admiral Yudo Margono told reporters on Saturday.

"The items would not have come outside the submarine if there was no external pressure or without damage to its torpedo launcher."

He said searchers found parts of a torpedo straightener, a grease bottle believed to be used to oil the periscope, pieces of prayer rugs and a section of a coolant pipe.

“With the authentic evidence we found believed to be from the submarine, we have now moved from the ‘sub miss’ phase to ‘sub sunk',” Adm Margono said at a press conference with the recovered items on display.

Military chief Hadi Tjahjanto said the presence of an oil slick as well as the discovery of debris were clear proof the vessel had sunk.

The cause of the disappearance is still unclear. The navy said an electrical failure could have left the submarine unable to execute emergency procedures to resurface.

Adm Margono said it was unlikely there had been an explosion.

“If it's an explosion, it will be in pieces. The cracks happened gradually in some parts when it went down from 300 metres to 400 metres to 500 metres ... If there was an explosion, it would be heard by the sonar."

The navy has said it believes the submarine sank to a depth of 600-700m, much deeper than its collapse depth of 200m, at which point water pressure would be greater than the hull could withstand.

The Bali Sea can reach depths of more than 1,500 metres.

Adm Margono said rescue teams from Indonesia and other countries would evaluate the findings. He said no bodies had been found so far. Officials previously said the submarine’s oxygen supply would have run out by early Saturday.

An American P-8 Poseidon reconnaissance plane arrived early Saturday and had been set to join the search, along with 20 Indonesian ships, a sonar-equipped Australian warship and four Indonesian aircraft.

Singaporean rescue ships were also due to arrive on Saturday, and Malaysian rescue vessels on Sunday.

The German-built diesel-powered submarine joined the Indonesian fleet in 1981, according to the defence ministry, and underwent a refit in South Korea, which was completed in 2012. It was said to be in good condition.

Indonesia operates five submarines – two German-built Type 209s including the Nanggala and three newer South Korean vessels.

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

With more than 17,000 islands, Indonesia has faced growing challenges to its maritime claims in recent years, including numerous incidents involving Chinese vessels near the Natuna islands north-west of Borneo.