Bali: At least 14 people are feared dead on the holiday island of Bali after the first heavy rain of the upcoming wet season caused some of the worst flash flooding locals have ever seen.

Combined with rubbish-blocked drains, the rain late on Tuesday and into Wednesday transformed small creeks and channels into raging torrents that collapsed buildings and caused traffic gridlock.

A building on the edge of the Badung River in Denpasar City collapses after being hit by the floods.

A building on the edge of the Badung River in Denpasar City collapses after being hit by the floods.Credit: Amilia Rosa

One taxi driver said it took five hours to complete the 20 kilometres from Canggu to the airport.

Tourist hotspots appeared to have escaped the worst of the floods, but a few low-lying areas were inundated. Video seen by this masthead showed some visitors travelling in a rescue boat over calm waters for higher ground. Others waded in knee-deep water.

Two people were confirmed to have died in the old area of Denpasar when rushing waters brought down an ageing four-storey building and parts of another, a moment caught on video.

Rescue workers hold grave fears for two more people still trapped in the debris. A further two survived and were being treated in hospital.

Authorities hold grave fears for more than ten people still unaccounted for in the Bali floods.

Authorities hold grave fears for more than ten people still unaccounted for in the Bali floods. Credit: AP

At a market near the collapsed building, at least one person was killed and two others were missing.

Rescue team leader Brama Budianto said the water level at 6.30am on Wednesday was the “highest we have ever witnessed”.