Floods and landslides in a central Indonesian province hit by torrential rain this week have killed 30 people and left more than two dozen missing, the national disaster agency said.

Key points: At least 25 people are reported missing

At least 25 people are reported missing More than 3,000 have been forced to leave their homes

More than 3,000 have been forced to leave their homes South Sulawesi's Governor said siltation of the dam and deforestation of the upstream watershed worsened the floods

Ten districts and cities in South Sulawesi province including the capital, Makassar, have been affected by flooding that began late on Tuesday, forcing more than 3,000 people to flee their homes.

Adnan Purichta Ichsann, the chief of Gowa district near Makassar, said operators of the Bili Bili rock-fill embankment dam were forced to release water on Tuesday, which contributed to flooding but avoided a worse disaster.

Residents push a motorbike in a flooded neighbourhood. ( AP: Masyudi Syachban Firmansyah )

South Sulawesi Governor Nurdin Adbullah told local media that siltation of the dam and deforestation of the upstream watershed worsened the floods.

One major highway has been blocked, prompting authorities to deliver aid via helicopter, according to media reports.

Aerial images showed muddy brown water covering swathes of land and, in some areas, washing away houses and debris.

National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said 30 people were confirmed dead and 25 were reported missing.

Residents ride a makeshift raft as they evacuate their flooded homes. ( AP: Masyudi Syachban Firmansyah )

Syamsibar, who goes by a single name and is the head of the provincial disaster agency, said the amount of rainfall was declining on Thursday and the Bili Bili dam's water level had dropped by about 2 metres.

Deadly landslides and floods are a frequent occurrence during seasonal rains in Indonesia, with man-made changes to the environment often worsening so-called natural disasters.

A landslide in Sukabumi on the country's most populous island of Java earlier this month killed 32 people.

AP