by Mynardo Macaraig

MANILA, Aug 7, 2012 (AFP) - Half of Manila was under water Tuesday, officials said, as torrential rains paralysed the Philippine capital in its worst floods since a typhoon killed more than 400 people three years ago.

Tens of thousands fled their homes as huge walls of water swept away houses, residents were stranded on rooftops and one slum was hit by a landslide, with at least 15 people confirmed killed in and near the city.

The deaths brought the number of people killed across the country from bad weather to 68 over the past week, according to civil defence officials.

Flood forecaster Gine Nievarez told AFP: "If we put it in a percentage, at least 50 percent of Metro Manila is flooded."

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

As local television flashed live footage of rampaging rivers carrying off houses and residents marooned on their rooftops, 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.

It is monsoon season in the Philippines and meteorologists said over half a month's rain fell on the capital in 24 hours.

The last time the capital was hit by major floods, from Typhoon Ketsana in 2009, more than 400 people were killed and the UN estimated the total damage from it and another storm at more than $4 billion.

Manila's population includes millions of squatters and residents of low-lying slums fled the huge shantytowns lining rivers and sewers overnight for the safety of schools, gymnasiums and government buildings.

Rosario Brutas, a market vendor in Bacoor, a town south of Manila, said she and her husband woke to discover their home already partly submerged.

"We woke up before dawn to find our bed afloat," the 32-year-old told AFP from a hospital courtyard where her family and their neighbours had taken refuge.

Army trucks hauled stranded residents from their homes, while power was turned off in some parts of the city as a precautionary measure with the waters seeping into electrical facilities, the city's power distributor said.

In some areas people were trapped on the second floor of their houses by the fast-rising waters, said Cora Agulan of the National Disaster Risk Reduction and Management Council.

She said there were many calls for help but in some areas it was too dangerous for rescuers to try to reach those stranded.

"The current is too strong so we have to tie our rubber boats with ropes to keep them from being swept away," she said.

Nine people from the same family were killed when a landslide struck a slum in the north of the city, officials said.

"The rain softened the soil and four houses were buried," said Maribel Mendoza of the local public safety office.

In nearby provinces also hit by floods, four people drowned in Bulacan and two were killed in Batangas.

Even before the deluge, the nationwide death toll from eight days of sustained rains had reached 53, with more than 268,000 people forced to flee their homes across the country, according to disaster authorities.

Weather forecaster Glaiza Escullar told AFP the heavy rains were expected to persist until at least early Wednesday.

Flood levels were close to but still lower than during Ketsana, she said, when "the water buildup was more abrupt and therefore more dangerous".

Manila had seen 323.4 millimetres of rainfall over the past 24 hours, she said, compared to Ketsana dumping 455 millimetres in the same period.

The capital's average August monthly rainfall is 504 millimetres.

The civil defence office said that while some 20,000 people fled to evacuation centres overnight, many more sought refuge in relatives' homes.