Indonesia, on Friday, intensified its search for a lost military submarine off the island of Bali with 53 people on board, while the US military sent a military force to participate in the search for the missing submarine.

Contact with the German submarine "KRI Nangala 402", about 95 km north of Bali, was lost in the early hours of Wednesday morning during training on a torpedo attack in which the 53 crew members participated.

A military official said Indonesian Submarine Fleet Commander Harry Sitiawan is among the 4 people on board the submarine who are not regular crew members.

The search for the missing submarine is focused on an oil slick in the north of Bali, where the submarine was floating for the last time before sinking under the water, according to the Indonesian Navy.

The Navy indicated that it is believed that the submarine is currently located at a depth of between 600 and 700 meters underwater, although it is designed to dive to depths ranging between 250 and 500 meters only.

Crew safety

"The main priority is the safety of the 53 crew members," President Joko Widodo said late last night, and called for all efforts to be made to find the missing 44-year-old submarine.

According to a spokesman for the armed forces, Ahmed Riad, the army has deployed 21 warships, including the submarine "KRI Aloguru" as part of a large operation to search for the submarine.

Riyadh confirmed in a press conference that the warships are supported by several civilian ships, one of which is equipped with sonar technology to detect underwater objects, and remote-controlled vehicles.

He said Singapore, Malaysia, Australia, India and the United States would also send rescue ships and aircraft to support the search operations.

The Navy explained on Thursday that the oxygen on board the submarine may continue until early Saturday.

"In the event of an electrical malfunction, the oxygen supply could last for about 72 hours," said Indonesian Navy Chief of Staff Admiral Yudo Margono.

"It can last until 3:00 am tomorrow, and we hope to be able to find the submarine before it runs out of oxygen," he added.

"We hope that we will not run out of oxygen before we find them," Margono told a news conference.

US support

In turn, the Pentagon announced yesterday that the US military will send an airborne military force to help Indonesia find the submarine.

"The US Department of Defense is deeply saddened by the loss of the Indonesian submarine during its participation in military exercises," Pentagon spokesman John Kirby said in a statement.

He added that, at the invitation of the Indonesian government, we will send military airborne personnel to help search for the missing submarine.

The spokesman said that US Defense Secretary Lloyd Austin will speak on Friday with his Indonesian counterpart Prabowo Subianto, to discuss other means that the United States can provide to help find the submarine.

According to the Ministry of Defense, the submarine - which weighs 1395 tons - was built in Germany in 1977, joined the Indonesian fleet in 1981, and underwent two years of maintenance that ended in 2012 in South Korea.