A heartbreaking video has emerged of the Indonesian submariners singing a lilting farewell love song in the weeks before their vessel broke open and sank deep into the Bali Sea last week.

In the emotional 21-second video released by the Indonesian Navy, crew members can be seen gathered around their captain Harry Oktavian in the conning tower near the periscope on the upper deck of KRI Nanggala-402.

One crew member begins playing an acoustic guitar before the submariners break into a rendition of Sampai Jumpa, an Indonesian song meaning “see you later”.

“Even though I’m not ready to be missing you, I’m not ready to live without you,” they sing.

“I wish all the best for you.”

The submarine was carrying 49 crew members, its commander and three gunners. Photo: Indonesian Navy

The 44-year-old vessel, with 53 crew on board lost contact last Wednesday as it prepared to conduct a torpedo drill. It was found on Sunday, broken into at least three parts, deep in the Bali Sea.

Rescuers initially spotted an oil slick and a few floating objects before a life jacket and other items were found, eventually leading to the discovery of the submarine at a depth of more than 800 metres.

“Based on the evidence, it can be stated that the KRI Nanggala has sunk and all of its crew have died,” military chief Marshal Hadi Tjahjanto told reporters on Sunday.

Navy chief of staff Yudo Margono said the crew were not to blame for the accident.

“The KRI Nanggala is divided into three parts, the hull of the ship, the stern of the ship, and the main parts are all separated, with the main part found cracked,” he said.

President Joko Widodo earlier confirmed the discovery in the Bali Sea and sent the families of the victims his condolences.

“All of us Indonesians express our deep sorrow over this tragedy, especially to the families of the submarine crew.”

Naval officers throw a flower garland into the sea at the port of Semarang on Monday. Photo: Getty

Earlier, search teams said on Saturday they had found objects including prayer mat fragments and a bottle of periscope lubricant near the submarine’s last known location, leading the navy to believe the vessel had cracked.

Mr Margono said a sonar scan had detected a submarine-like object at 850 metres, beyond the Nanggala’s diving range.

More than a dozen helicopters and ships searched the area where contact was lost, with the United States, Australia, Singapore, Malaysia, and India providing assistance.

Grieving Ceci Yuemi (R) with family members offer prayers as she sits with a photo of her husband, Second Lieutenant Munawir, who served onboard the submarine at a religious gathering in Surabaya on Monday. Photo: Getty

Residents of the East Java town of Banyuwangi, which hosts the naval base from where search and rescue operations are being conducted, joined nationwide calls to accelerate the modernisation of Indonesia’s defence forces.

“This can be a learning point for the government to advance its military technology and be careful in how it uses its (existing) technology because its people’s lives are at stake,” said 29-year-old resident Hein Ferdy Sentoso.

Southeast Asia’s most-populous country has sought to revamp its military capability, yet some equipment is still old and there have been fatal accidents in recent years.

Indonesia had five submarines before the latest accident; two German-built Type 209s including Nanggala and three newer South Korean vessels.

-with agencies