Indonesia's air force seeded clouds with salt on Friday to try to stop rainfall reaching the slowly sinking capital after deadly flash floods and landslides triggered by some of the heaviest rain ever recorded.

The death toll in Jakarta and surrounding areas rose to 43 as of Friday, the disaster mitigation agency said, while tens of thousands of people have been displaced.

Indonesia's technology agency BPPT and the air force carried out three rounds of cloud seeding on Friday, with more expected when needed, a BPPT official said. The seeding, shooting salt flares in an attempt to trigger rainfall, is aimed at breaking up clouds before they reach Jakarta.

"We will do cloud seeding every day as needed," BPPT chief Hammam Riza told reporters.

Cloud seeding is often used in Indonesia to put out forest fires during the dry season.

The floods followed torrential rains on Dec. 31 and into the early hours of New Year's Day that inundated swathes of Jakarta and nearby towns, home to about 30 million people.