Tens of thousands of people were evacuated in Indonesia's capital Jakarta on Thursday after flash floods and landslides killed up to 26 people amid some of the heaviest rain in more than 20 years, with more deluges forecast, authorities said.

The flooding, among the deadliest in years, caused chaos in parts of Southeast Asia's biggest city with train lines blocked and power outages in some areas.

Swathes of Jakarta and nearby towns were inundated after heavy rain fell on December 31 and into the early hours of New Year's Day.

Social affairs ministry data showed 26 people were killed in the flooding, up from the earlier toll of 21. As of Thursday morning, over 62,000 people were evacuated in Jakarta alone, disaster mitigation agency spokesman Agus Wibowo said, although later in the day he told news channel Metro TV the number of evacuees were down to around 35,000 people.

Rainfall at an airport in East Jakarta measured at 377 millimeters (15 inches) early on January 1, the highest daily reading during major floods since at least 1996, according to the Meteorology, Climatology and Geophysics Agency (BMKG).

Umar Dani, 52, and his family were evacuated overnight from his home in East Jakarta on a rubber boat after water levels rose up to his neck.