Stephen Fitzpatrick, Jakarta – Dozens have been confirmed dead and many more are still missing after a reservoir wall collapsed in the Indonesian capital, creating a "tsunami" that wiped out an entire suburban area.

The disaster, in South Jakarta only a few kilometres from the city centre, occurred at about 2am yesterday (6am AEST) after hours of heavy monsoonal rain.

The picturesque university residential district of Cireundeu was a disaster scene after the Situ Gintung lake, a popular tourist spot covering an area of 21ha, broke its banks.

The death toll had reached 77 on Saturday with many more still missing. The search and rescue agency which is keeping the death toll said the number keeps climbing.

Local police chief Captain Ngisa Asngari said on Saturday that hundreds of soldiers, police and volunteers were digging through piles of mud and debris in search of survivors or more bodies.

One survivor described the experience as "just like being in a tsunami", with water surges reaching several metres while victims slept. Many people are believed to have died without waking, their houses destroyed in the brute force of the tide.

A second wall collapse occurred at about midday, with more houses destroyed.

Hospitals were struggling to cope with the arrival of dozens of dead and injured, and with hysterical residents searching for family members.

President Susilo Bambang Yudhoyono, on the campaign trail for elections just two weeks away, arrived at the area about noon on the back of one of his military police outrider's motorbikes, after his convoy was trapped in gridlock traffic caused by the disaster.

The devastated area stretched for about 5km from the lake, and there were fears last night that more rain would make the situation worse.

One resident, Minu, told the online news service Detik.com her household was fast asleep when the lake burst. Suddenly, she said, there was a great commotion and the screaming of people.

"They were shouting, 'The water's coming in, the water's coming in', and our dogs were barking," she said.

She heard what she thought was someone knocking on the door of her house, until she realised it was the rushing water. Minu said she gathered her family and household staff and rushed to the upper floor of the home to await rescue.

She said a neighbour in her Cireundeu Permai housing estate narrowly escaped with his life after trying to escape by car.

"At the moment the water swept through, he immediately ran to the garage and tried to get his car out, but the water was already rising and the engine wouldn't start, so that suddenly the water was too high. He got out of the car by smashing the front windscreen," she said.

Other residents said they had been aware of cracking in the lake's retaining wall from about midnight, with heavy rain having fallen since the previous afternoon. A Dutch-era brick bridge was swept away before the wall collapsed.

Search and rescue personnel, as well as nearby residents, used rubber boats to rescue those they could, with hundreds of homes destroyed.

Deputy President Jusuf Kalla, who visited the area with Co-ordinating Minister for People's Welfare Abu Rizal Bakrie, said the Government would "provide emergency help to the victims. For those whose homes were destroyed, the Government will help with the repairs."

Danang Susanto, an official at the Health Ministry's crisis centre, said at least four children were among confirmed victims. All of them drowned, he said.

"Right now, residents are being evacuated. About half of them are still on rooftops waiting for help," said crisis centre chief Rustam Pakaya.

Survivors were being evacuated to dry ground at the nearby Muhammadiyah University and in local schools. A worker at Jakarta's Fatmawati hospital, Roni, said the hospital had received the bodies of four victims, including a nine-year-old girl. They were all blue and covered in mud. The nine-year-old had been found on the roof with head injuries, she said.

Houses and concrete buildings were buckled by the force of the waters as they swept through the neighbourhood, a mix of large middle-class homes in comfortable gated communities and crowded traditional kampungs, or urban villages.

"The floods caused a landslide, destroying my house and another one below it," local resident Mabruri told TV One. "Whenever it rains, water rises. But never like this."