At least 73 people were killed and more than 330,000 others displaced after the heaviest rain in more than four decades plunged the Philippine capital into turmoil, officials said Sunday.

The nine-hour deluge across Manila on Saturday submerged houses, washed away shanties and turned roads into raging rivers, forcing terrified residents to seek refuge on top of homes or cars where they waited for more than 24 hours.

"I am calling on our countrymen... to please stay calm," President Gloria Arroyo said, as she set a deadline of nightfall on Sunday for the military and other rescuers to save those who remained stranded.

The frantic rescue efforts saw military helicopters and rubber boats fan out across the sprawling city of 12 million residents to pluck people off houses and car roofs.

The US military contributed a helicopter and six boats to the operations.

The downpour from tropical storm Ketsana left some areas of Manila under up to six metres of water, shocking a country that is already used to being battered by typhoons with its ferocity.

"This is the worst (flooding) that I have seen," Defence Secretary Gilberto Teodoro said.

Teodoro, who is co-ordinating the rescue efforts, said 73 people had been confirmed killed with at least 23 others still missing.

Nearly 280,000 people in Manila and five outlying provinces were displaced, with more than 41,000 victims already placed in evacuation centres, according to Teodoro.

"We are continuing with our rescue operations for those who are still in need, coupled with a massive relief operation," said Teodoro.

While the rains have temporarily ceased, Teodoro said more flooding may hit northern provinces as reservoirs and dams could overflow.

"I am appealing on those in the path of the storm to follow our local officials," he said, adding that troops will forcibly evacuate those who refuse to leave their homes being threatened by floods.

He said the floodwaters and the large numbers of stranded vehicles were giving rescue units "a hard time" in reaching those affected.

"If you are on the roof, don't try to leave. Just remain there on the roof and we will do everything to rescue you," he said in a radio broadcast.

Metropolitan Manila under water

Power and communication lines went down in many areas but those who managed to get through to public radio stations told of their plight.

"Please come and get us. We have been marooned here since the afternoon," appealed Cristine Reyes, a resident in Marikina district late Saturday, who was marooned with her two young nephews and her mother on the second floor of the family home. "The water continues to go up, and soon we will be under water."

Local Red Cross chairwoman Gwendolyn Pang said rescuers struggled to reach many areas Saturday, with many highways rendered impassable.

"This has never happened before. Almost 80 percent of metropolitan Manila is under water," Pang told AFP.

The government's chief weather forecaster Prisco Nilo blamed "climate change" for the extreme weather but said he expected the weather to ease when the storm dies down Monday.

"The amount of rainfall in nine hours yesterday was more than the average monthly rainfall," Nilo told reporters.

He said that total rainfall for the period reached 410.6 millimetres, breaking the previous single-day record of 334 millimetres in July 1967.

In Marikina Sunday, many residents remained on rooftops, as rescuers waded in muddy floodwaters, Red Cross official Dave Barnuevo said.

"The water is taking a long time to go down. The water is muddy and thick, and we have had to push our rubber boats in neck-deep flood(waters) in some areas," Barnuevo told AFP.

"We have rescued entire families marooned in their homes. They have not eaten and begged for food and water," he said.

- AFP