The oxygen supply for the 53 crew members of an Indonesian navy submarine missing in waters off Bali is believed to have run out, with no sign of the vessel.

Rescue teams from several countries have been battling against time to find the KRI Nanggala 402 which went missing during a training exercise in waters north of the island of Bali.

The 43-year-old sub was conducting a torpedo drill on Wednesday but failed to relay the results as expected and has been silent ever since.

Navy chief of staff Yudo Margono said the submarine was expected to run out of oxygen at 3am on Saturday local time – 8pm on Friday GMT.

There have been no signs of life from the submarine, but family members have been holding out hope that the large search effort would find the vessel in time.

Ratih Wardhani, the sister of 49-year-old crewman Wisnu Subiyantoro, said: “The family is in a good condition and keeps praying.

“We are optimistic that the Nanggala can be rescued with all the crew.”

More from Indonesia

Berda Asmara, the wife of crew member Guntur Ari Prasetyo, 39, said when she last spoke to her husband before he set sail he “asked me to pray for him”.

She added: “I hope that they will be found alive.”

Indonesia’s navy said it was investigating whether the sub lost power during a dive and could not carry out emergency procedures as it descended to a depth of 600-700m (1,970ft-2,300ft), well beyond its survivable limits.

However, on Thursday an object with “high magnetic force” had been spotted “floating” at a depth of 50-100m (164ft-328ft), and an aerial search had earlier spotted an oil spill near the submarine’s last location.

The Bali Sea can reach depths of more than 1,500m (4,921ft)

Indonesian President Joko Widodo asked Indonesians to pray for the crew’s safe return.

“Our main priority is the safety of the 53 crew members,” Mr Widodo said in a televised address on Thursday.

“To the family of the crew members, I can understand your feelings and we are doing our best to save all crew members on board.”

The submarine joined the Indonesian fleet in 1981, according to the defence ministry, and underwent a refit in South Korea completed in 2012.

It was said to be in good condition.