The death toll from floods and landslides in Indonesia's South Sulawesi province has jumped to at least 59, according to authorities, as rescuers raced to find more than two dozen others still missing.

Some 3,400 people were evacuated from their homes as heavy rainfall and strong winds pounded the southern part of Sulawesi island on Wednesday and Thursday, swelling rivers that burst their banks and inundating dozens of communities in nine districts.

"I've never seen something this bad - this is the worst," Syamsibar, head of South Sulawesi's disaster mitigation agency, told AFP news agency on Friday, adding that 25 people were still missing.

The death toll was 30 on Thursday evening.

Gowa district suffered the heaviest casualties, with 44 people found dead, said Syamsibar, who like many Indonesians goes by one name.

One major highway was blocked, prompting authorities to deliver aid via helicopter, according to local media. Parts of the provincial capital, Makassar, were also affected.

Aerial images showed muddy brown water covering swaths of lands and, in some areas, rushing water washing away houses and debris.

Those evacuated were given refuge in schools, mosques and tents. At least 46 are being treated at local hospitals and health clinics.

Search ongoing

Residents waded through streets filled with waist-deep water, some carrying their belongings on their heads, as they fled to temporary shelters and field kitchens set up by the disaster mitigation agency.

On Thursday, the agency said that while flooding in the province was receding "the search and evacuation process is still ongoing".

"We urge people to always be aware of the possibility of floods and landslides," Sutopo Purwo Nugroho, spokesman for the national disaster agency, said.

The floods also damaged houses, government buildings, schools and bridges.

Landslides and flooding are common in disaster-prone Indonesia, especially during the monsoon season between October and April, when rain lashes the vast Southeast Asian archipelago.

In October, flash floods and landslides killed at least 22 people in several districts across Sumatra island.