Indonesia has deployed six warships to search a navy submarine that went missing with 53 people on board.
A helicopter and 400 people were also sent out on the hunt, the navy said.
Singapore and Malaysia have also dispatched rescue ships, while the US, Australia, France and Germany have offered help.
The KRI Nanggala-402 vessel had been conducting a drill north of the island of Bali on Wednesday, but failed to report back and contact was lost.
The German-made submarine is thought to have disappeared in waters about 100km off the coast of Bali early on Wednesday morning.
First Admiral Julius Widjojono told media that the navy is searching for it.
He said the navy is familiar with the area but it’s quite deep.
Some reports suggest that contact was lost after the submarine had been given clearance to dive into deeper waters.
Meanwhile, an oil spill found near where a missing submarine dived could point to fuel tank damage, or could also be a signal from the crew, the Indonesian navy said.The submarine is one of five vessels operated by Indonesia navy. It was made in the late 1970s, and underwent overhaul that was completed in 2012.
It is the first time Indonesia has lost one of its submarines, a navy spokesman told the BBC.
But similar incidents have happened elsewhere. In 2017, an Argentine military submarine went missing in the southern Atlantic with 44 crew on board.
Its wreck was located a year later, and officials confirmed that the submarine had imploded.