MANILA - Half of Manila was under water and 250,000 people fled their homes Tuesday as torrential rain paralysed the city, sweeping away houses, leaving residents stranded on rooftops and triggering a landslide.

At least 15 people were confirmed dead as the sprawling metropolis and nearby provinces suffered the most extensive floods since a typhoon that killed hundreds three years ago.

Schools, financial markets and most government and private offices were shut as key roadways in the capital -- a city of some 15 million people -- were submerged by waters that in some areas reached neck-deep.

"If we put it in a percentage, at least 50 per cent of Metro Manila is flooded," Gine Nievarez from the state weather service told AFP.

As local television flashed live footage of rampaging rivers carrying off houses and residents marooned on the roofs of their homes, President Benigno Aquino said the government was doing everything it could to help.

"Everybody who is supposed to do something is doing what he is supposed to do," he told reporters after meeting with civil defence officials.

Bad weather from seasonal southwest monsoons has been pounding Manila and nearby areas for over a week. Meteorologists said the crisis in the capital came as over half a month's rain fell on the city in 24 hours.