Torrential rains in the Philippines have forced nearly 20,000 people into makeshift camps closing schools, offices and the stock exchange.

Residents in eastern Manila, the capital, were evacuated on boats after authorities put nine provinces on alert due to severe flooding, with water rising heavily in some areas.

Flood waters reached up to two metres, shutting down entire city blocks on Tuesday.

At least 51 people have died in week long rains throughout the Philippines from Typhoon Saola.

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.

Residents of low-lying slums fled the huge shantytowns lining Manila's rivers and sewers for the safety of schools, gymnasiums and government buildings as the downpour generated by seasonal monsoons struck overnight.