Philippine officials say that at least 16 people have died in severe floods in the capital, Manila.
More than 80,000 people are in emergency shelters, as torrential rain left low-lying areas under water.
Soldiers and rescuers are using rubber boats to reach people stranded in their homes, but some are refusing to leave amid fears of looting.
The flooding – neck-deep in some parts of the city – forced the closure of offices and schools around the city.
More than half the amount of rain normally seen in August has fallen in the capital in 24 hours, reports say.
In the worst reported incident of casualties, nine members of one family died after a landslide hit shanty houses in Manila’s Quezon City.
Others died from drowning and electrocution, according to the country’s disaster response agency. A state of calamity has been issued in at least four areas, it added.
“We’re still on a rescue mode,” said Benito Ramos, head of the country’s disaster response agency.
“Floods are receding in many areas but people are still trapped on their roofs.”
President Benigno Aquino called for the public’s co-operation, warning that the government did not have “infinite capabilities” to deal with the natural disaster.
People are said to be stranded in homes all over the city.
Soldiers, police and volunteers are trying to reach them by boat, but some people are refusing to leave, scared their possessions will be taken by looters.
“The flooding has impacted everyone here. Even if your house did not flood – and ours didn’t – the streets flooded badly and so much of Manila has been impassable and people have been stranded,” said Julie Green, an Australian currently living in Manila.
“All businesses have been closed except for 7-11s and some sari-sari [convenience] stores. Everyone’s stocks are getting quite low now so you have to wake up early and battle the rains to get some food.
“It rained hard again all last night, but it seems now that the rains might have abated. People are starting to come out again.”
Officials have warned that more rain is expected, however, and are urging people to consider their safety first.
Manila and the northern Philippines have been hit by severe weather since Typhoon Saola struck just over a week ago, killing more than 50 people.
The government is better prepared this time than when typhoons hit the country previously – tens of thousands of people have been evacuated, says our correspondent.
Typhoon Ketsana hit the Philippines in September 2009, causing flooding that killed more than 400 people and Typhoon Nestat and Nalgae struck two years later, leaving more than 100 dead.
The current rain and floods are said to be the worst to hit the country since 2009. However, the state weather bureau has said that weather conditions may get better later this week.