Indonesia’s Defence Ministry said contact could not be re-established with the submarine after it requested permission to undertake a diving manoeuvre at 3am local time[6am AEST] on Wednesday. Indonesian media said the navy believed the submarine had descended to a depth of 700 metres,well beneath its capacity.

“A search by other vessels involved in the drilling taskforce was then in action,” the ministry said.

“At 7am Western Indonesia Time from aerial observation by the helicopter,it was found that there was an oil spill around the position of the initial diving.”

Indonesian warships have also been sent to the area from where the 1400-tonne submarine was last heard.

The ministry said there were 49 crew on the vessel as well as three gunners and its commander.

“The search continues until now by KRI Rigel from Jakarta and KRI Rengan from the Mine Unit by using side scan sonar,” the ministry said.

“Some countries have responded and are ready to provide assistance. Some of them are the Singaporean navy and Australian navy.”

Singapore’s submarine rescue vessel,MV Swift Rescue,was reported to have been dispatched to the waters north of Bali from Changi naval base.

Built in 1979,the KRI Nanggala-402 is one of five submarines in Indonesia’s fleet and had been practising for a torpedo firing drill off the coast of Bali on Thursday.

The vessel is one of two Type 209/1300 submarines owned by the Indonesian navy that began service in 1981. They were refurbished in South Korea a decade ago.

It was only last month that Indonesian Defence Minister Prabowo Subianto unveiled the country’s newest submarine,the third of three more modern Nagapasa-class subs manufactured by South Korea’s Daewoo Shipbuilding that round out the country’s fleet. Built in Indonesia itself,it was the first submarine to be assembled in south-east Asia.

“We realise together how important our defence is,” Prabowo said at the launch in in Surabaya,Indonesia’s second-largest city.

“We are building our defence capabilities. Not because we want to be brave. Not because we want to threaten anyone. Over and over again,it has been passed down from the founder of our nation,we have emphasised that the Indonesian nation loves peace but loves independence more.”

The Australian Defence Force has been contacted for comment.

Tjahjanto,the Indonesian defence chief,is due to hold a news conference on Thursday afternoon (AEST).

with Sarah McPhee