At least 21 people have died in flooding in the Indonesian capital, Jakarta, after the city had its most intense rainfall for at least 24 years.

The Meteorology, Climatology and Geophysics Agency (BMKG) measured 377 millimetres of rainfall in a day at an airport in East Jakarta.

That's the most most rain in a single day since at least 1996, when records supplied by the agency began.

"The rain falling on New Year's Eve... is not ordinary rain," said the agency.

The agency said the intensity of the rain was due to several factors including the monsoon season as well as a high amount of water vapour in the air affecting cloud formations over Java island.

The heavy rainfall is expected to continue until the weekend.

Elsewhere in East Jakarta, 335mm was recorded, while in Bekasi, further east, 259mm fell.

Rainfall above 150mm per day is considered extreme by the agency.

Maximum rainfall intensity during major Jakarta floods

© Meteorology, Climatology and Geophysics Agency (BMKG)

The intense rain began on New Year's Eve and continued through the night leading to parts of the city being submerged and landslides on the outskirts.

The victims ranged in age from 8 to 82. Some died of hypothermia, while others drowned or were killed by landslides. Two of the dead are from Lebak, south-west of the capital.

One 16-year-old boy was electrocuted by a power line.

As many as 47 people have now died as a result of the massive flooding in Jakarta Metropolitan Area in Indonesia on 01 January, 2020. Indonesia's National Disaster Mitigation Agency (BNPB) said that 409,000 people have been affected by the floods, with over 366,000 of them in Bekasi City.

© BNPBThousands have been displaced after massive flooding in Jakarta, Indonesia, 01 January 2020.

National Disaster Mitigation Agency (BNPB) reported 11 deaths in Bogor City, 11 in Bogor Regency, 7 in East Jakarta, 7 in Lebak Regency, 3 in Depok City and 3 in Bekasi City. Other fatalities occurred in Tengarang, South Tangerang, Bekasi Regency and Central and West Jakarta. One person is still missing in Lebak Regency. BNPB said the deaths were a result of hypothermia, electric shock, landslides and drowning in flood waters.

Dozens of locations across Jakarta Metropolitan Area were flooded. As of 02 January, authorities reported that flooding had started to recede in some areas. The number of displaced has fallen from an estimated 62,000 people to around 22,000. Meanwhile search and rescue teams continue to rescue dozens of people trapped in flooded buildings in affected areas.

BNPB said that Indonesia's Agency for the Assessment and Application of Technology (Badan Pengkajian dan Penerapan Teknologi - BPPT) plans to use weather modification technology in an attempt to reduce the rainfall in the Greater Jakarta area to prevent additional flooding.