Rescue workers are being overwhelmed by the scale of floods in the Philippines that are estimated to have killed at least 140 people, officials say.
The head of the National Disaster Co-ordinating Council, Anthony Golez, said resources were being spread too thinly.
Torrential rains from Tropical Storm Ketsana flooded the capital, Manila, and 25 nearby provinces on Saturday.
Some 80% of Manila was submerged, displacing 450,000 people. More than 115,000 are now in makeshift shelters.
"We are concentrating on massive relief operations. The system is overwhelmed, local government units are overwhelmed," Mr Golez told reporters.
"We were used to helping one city, one or two provinces but now, they are following one after another. Our assets and people are spread too thinly."
One doctor in Manila told the BBC that he had been working 24-hour shifts in a hospital flooded with water since Saturday.
Defence Minister Gilbert Teodoro said troops, police and volunteers had so far been able to rescue more than 7,900 people. Thirty-two people are missing.
The authorities were now focusing on providing food, medicine and other necessities to those in emergency shelters, he added. Telephone and power services in some parts of Manila remain cut.
Over the weekend, the government declared a "state of calamity" in Manila and the 25 storm-hit provinces, including many that have not experienced widespread flooding before, allowing access to emergency funds.
The Philippine government has not yet requested international help, but Mr Golez said it would welcome any assistance. The US military has deployed a helicopter and soldiers to the country's south to help.
On Sunday, President Gloria Arroyo visited the devastated areas, appealing for calm over what she described as an "extreme event" that "strained our response capabilities to the limit but ultimately did not break us".
Ramil Digal Culle in Cavite City, south of Manila, told the BBC that he had spent the night with families trapped on rooftops without food and water.
"The mothers were at work when the flooding happened and they got stranded with me, unable to go home," he wrote in an e-mail.
"Strange how I could have internet access during the disaster to describe this experience... while the government struggles with a scarcity of rescue equipment," he added.
Some officials are quoted as saying rubbish-choked drains and waterways, along with high tides, compounded the flooding.
The BBC's Alastair Leithead in Marikina City, the worst affected part of the capital, says all the streets in the area were under metres of water and that now there is a thick coating of mud over everything which was submerged.
Our correspondent says the government argues it could not have been expected to cope easily with a storm in which a month's rain fell in 12 hours.
In the meantime, he adds, people are just focusing on clearing up, trying to salvage what possessions they can, along with food, water and some shelter, because further rainstorms are forecast.
Reports have also emerged of acts of heroism by members of the public during the floods, including Muelmar Magallanes, who rescued more than 30 people, but ended up sacrificing his own life.
With the help of his older brother, the 18-year-old construction worker tied rope around his waist and took his siblings to safety before going back to the house for his parents, according to the AFP news agency.
Later, he decided go back to save neighbours trapped on rooftops. He then dived back in again when he saw a mother and her six-month-old baby daughter in the water.
"I didn't know that the current was so strong. In an instant, I was under water. We were going to die," the mother Menchie Penalosa told AFP.
"Then this man came from nowhere and grabbed us. He took us to where the other neighbours were, and then he was gone," she added.
Witnesses said an exhausted Mr Megallanes was simply swept away by the water.
His father Samuel said: "He always had a good heart. We had already been saved. But he decided to go back one last time for the girl."
The Philippines chief weather forecaster, Nathaniel Cruz, said more than 40cm (16in) of rain fell on Manila within 12 hours on Saturday, exceeding the 39cm average for the whole month of September.
The previous record of just over 33cm in a 24-hour period was set in June 1967, Mr Cruz added. He had earlier blamed climate change for the mass downpours.
Ketsana, with winds of up to 100km/h (62mph), hit the Philippines early on Saturday, crossing the main northern Luzon island before heading out toward the South China Sea.