Manila: At least a dozen residents were killed, mostly the children and the elderly, after flashfloods struck a residential area in Davao City just past midnight on Wednesday.

An official report issued by the National Disaster Risk Reduction and Management Council (NDRRMC) placed the official number of fatalities from the flooding at 11, while unnoficial information stated the number of deaths to as high as 21.

According to the NDRRMC, record high flashfloods occurred in five villages in Davao City, namely Maa, Matina Pangi (Samantha Homes), Matina Crossing, Talomo Proper and Matina Aplaya between 11 pm Tuesday and early morning Wednesday.

Although Davao City had been largely free from destructive flooding, a six-hour non-strop heavy downpour that started at 9pm caused the Pangi River and Matina River to overflow, inundating several areas.

"Davao City experienced the highest level of floodwaters to date reaching up to 10 feet (3.4 metres) high," a report released by Undersecretary Benito Ramos, Executive Director of the NDRRMC said, adding that at around 5 am Wednesday, the water level had already subsided.

A report by the ABS-CBN network said that in some parts of residental Davao City the floodwaters were as deep as 10 metres.

The five areas affected were largely lower-middle class areas with single level houses, an estimated 5,250 families had been affected by the flooding

"At the height of the flooding, affected residents sought shelter at the GSIS covered court in Central Park Subdivision," the report said as it referred to an elevated area at the Government Service Insurance System (GSIS) village, an old residential district in Davao City.

Raging floodwaters also damaged the Balusong Cridge in Matina Crossing.

The age of the fatalities ranged from three years old to 65, but most of the deaths were children.

Davao City Mayor Sara Duterte-Carpio was quoted in reports as saying that most of the residents in the affected areas were caught unprepared for the flooding. She said most of the flooded residents had to clamber up the rooftops of their single-level homes or climb up trees to save themselves from getting drowned.

Some of the residents were rescued by emergency services units of Davao City such as the 911 Urban Search and Rescue Unit, the police public safety batallion, the Philippine Air Force and the Coast Guard.

Duterte-Carpio said four of the affected villages have were placed under a state of calamity to hasten the release of relief funds.

Science and Technology Undersecretary Graciano Yumul explained that an isolated thunderstorm had caused the sudden heavy downpour. He warned that similar flashfloods can occur in other areas of Davao City.

Davao City, located some 1,500 kilometres south of Manila, is considered as the biggest city in the country and one of the most progressive.