The floods, triggered by heavy rain on Saturday, hit two separate parts of Nduga regency in the eastern province of Papua Pegunungan.

As of Tuesday, "23 people are still declared missing by the local disaster agency," including 15 who were swept away by a flash flood while attempting to cross a river, Abdul Muhari, spokesman for the national agency, said in a statement.

"The search and rescue efforts... are ongoing after the flash flood," Abdul said, adding that massive landslides in the area have hampered the operation.

The annual monsoon season in Indonesia, typically between November and April, often brings landslides, flash floods and water-borne diseases.

Climate change has affected storm patterns, including the length and severity of the season, leading to heavier rain, flash flooding and stronger wind gusts.

At least 18 people died in September when a flood hit Bali -- the popular holiday island's worst in a decade, according to the Meteorology, Climatology and Geophysics Agency.

In January, floods and landslides in Central Java province killed at least 25 people.