The death toll from the massive flooding in the Philippines has climbed to 246 people, officials said late Tuesday, and now there are fears about more storms due to hit the area later this week.

Tropical Storm Ketsana, which sliced across the northern Philippines on Saturday, dumped more than a month's worth of rain in just 12 hours. It has led to the worst flooding to hit the country in more than 40 years. About 80 per cent of Manila, a city of 15 million, was flooded.

The National Disaster Coordinating Council said Tuesday the homes of nearly 1.9 million people had been flooded, and nearly 380,000 people had been brought to schools, churches and other evacuation centres.

Officials called in extra police to prevent looting in neighbourhoods left empty by fleeing residents.

After hammering the Philippines, the storm gathered strength over the South China Sea early in the week before making landfall Tuesday in Vietnam, where it killed 23 people. Officials said the storm is weakening as it travels toward Laos.

More storms are brewing in the Pacific Ocean east of the country. One could hit the northern island of Luzon Friday and the other early next week. But meteorologists say that could still change.

More than 12,400 people have been rescued in the Philippines so far, but many survivors are reporting that more bodies lie under the water of the swollen rivers and debris-strewn streets.

Troops and police are getting the help of dozens of volunteers in their search for survivors. Even the country's communist guerrillas announced a ceasefire, saying they will hold off on assaults against government forces for now to help villagers recover from the storm.

Overwhelmed officials are also calling for international help, warning they are going to run out of resources. Defence Secretary Gilbert Teodoro told a news conference Tuesday that help from foreign governments will ensure that the Philippine government can continue its relief work.

"We are trying our level best to provide basic necessities, but the potential for a more serious situation is there," Teodoro said. "We cannot wait for that to happen."

The government declared a "state of calamity" in Manila and in 25 provinces, which allows officials to tap into emergency funds to deliver aid and conduct search-and-rescue efforts.

Volunteers handed out bottles of water and other items to survivors, while others began mopping up water, which had receded considerably by Tuesday morning.

Power was cut in a number of communities, some of which were left covered in mud.

In the Bagong Silangan district of Manila, about 150 people took shelter in a covered basketball court, lying on pieces of cardboard with what few belongings they had piled around them.

A number of evacuees complained that too little aid was being offered, and too slowly.

President Gloria Macapagal Arroyo pleaded for patience as her government tackles the aftermath of one of the worst storms to hit the region.

"We're responding to the extent we can to this once-in-a-lifetime typhoon emergency," she said in a statement Tuesday.

Arroyo opened part of the presidential palace as a relief centre, where hundreds of residents received packets of noodles and other food. Arroyo's executive chef cooked food for victims at another relief centre.

The president announced that she and members of her Cabinet will donate two months' salary to the relief effort.

Teodoro estimated damage from the storm so far at around US$98.5 million, but those figures will surely increase as reports come in from remote areas.

"Even opportunity loss of revenues for establishments, that alone would amount to hundreds of millions at least per day," he said.

The United States has donated $100,000 and deployed a military helicopter and five rubber boats manned by about 20 American soldiers from the country's south, where they have been providing counterterrorism training.

Unicef, the United Nations Children's Fund and the World Food Programme have also provided food and other aid.