Torrential rains brought the Philippines capital to a standstill Tuesday, forcing at least 20,000 people to flee their homes as floodwaters covered half the sprawling city, authorities said. Schools, financial markets and most government offices were shut as key roadways in Manila -- a metropolis of some 15 million people -- were made impassable by waters that in some areas reached neck-deep. Residents of low-lying slums fled the huge shantytowns lining Manila\'s rivers and sewers for the safety of schools, gymnasiums and government buildings, the civil defence office said. Jean Navarez from the state weather service warned that the floods generated by seasonal monsoon rains could worsen as the La Mesa dam, Manila\'s sole reservoir, began letting off water. \"If we put it in a percentage, at least 50 percent of Metro Manila is flooded,\" she told AFP. \"There will be heavy rainfall for the next 24 hours. The floods will increase,\" she added. The National Disaster Risk Reduction and Management Council said that while some 20,000 people fled to evacuation centres overnight, many more sought refuge in relatives\' homes. The La Mesa dam overflow, which has swelled nearby rivers, and a high tide on Manila Bay conspired to worsen the flooding, it said. Bad weather from seasonal southwest monsoons has pounded Manila and nearby areas for over a week since Typhoon Saola brushed past the country\'s north. The death toll from eight days of sustained rains has risen to 53 with more than 268,000 people forced to flee their homes across the country, according to disaster authorities.