Are you affected by severe weather? Send photos and stories to CNN iReport.
Manila, Philippines (CNN) -- Fueled by seasonal monsoon rains and a nearby tropical storm, widespread flooding in the Philippines worsened Tuesday, killing at least 11 people, the national disaster agency reported.
A landslide in the Manila suburb of Quezon City buried two houses, leaving nine people dead and four others injured, according to the National Disaster Risk Reduction and Management Center.
Three of the dead were children, the state-run Philippines News Agency reported.
The capital city of Manila got 504 millimeters (about 20 inches) of rain Tuesday, PNA reported, with more on the way.
The country's weather service -- the Philippine Atmospheric, Geophysical and Astronomical Services Administration -- warned the Manila region's 12 million residents of continued torrential rains and serious flooding through Wednesday.
"It's like a water world," Benito Ramos, head of the disaster agency, said of the city, according to PNA.
The national railroad called off service, and many roads were under water. Some dams were beginning to overflow, putting more communities at risk, the authorities said.
The flooding has already forced more than 780,000 people across the country from their homes, the disaster agency said. About 242,000 were staying in emergency shelters Tuesday night, according to the agency.
Rescue requests continued to come in early Wednesday, including some people who were using Twitter to contact the authorities for help.
"Pregnant woman needs help! Staying on top of a roof," one Twitter user posted, followed by an address. "Please help BORRES FAMILY w/ 2y/o child!!," posted another.
The weather agency warned residents to expect more landslides and flash flooding, and the authorities urged residents in low-lying areas to move to higher ground.
As well as the deaths in the landslide in Quezon City, two people died from electrocution and drowning outside the Manila region, the disaster agency said early Wednesday.
Those deaths came on top of the 53 people who had already been killed across the Philippines by heavy wind and rain in the past few weeks.
In an effort to save lives and make way for rescue and relief efforts, President Benigno Aquino ordered work suspended at government and private offices around the capital region Tuesday.
Government offices and schools were also to be closed Wednesday, the president's office said.
Deep water in many parts of metropolitan Manila blocked roads, stranded cars and flooded homes. In several areas, the water was waist deep or higher, the Metropolitan Manila Development Authority said in its Twitter feed.
"Last night it was raining cats and dogs, or even like elephants banging on your roof top," said CNN iReporter Rummel Pinera. "You cannot sleep when it's raining for several hours like this, it was like a deluge."
Another iReporter, Jumar Rejuso, said the downpour was terrifying.
"We had to force ourselves to leave in order to be spared from the wrath of the raging waters," he said. "It was the first time I have witnessed in my entire life a flood as big as that."
Flooding has struck across the Philippines, with high water reported in 46 communities across the country, the disaster agency reported.
The authorities in Marikina City imposed a forced evacuation of areas near the Marikina River, which has risen above critical levels, PNA reported.
The National Disaster Risk Reduction and Management Council said the Ambuklao, Binga and San Roque dams were releasing water, putting several cities at a higher risk of flooding. The agency warned residents living near the dams to be on the lookout for rising waters.
U.S. Ambassador to the Philippines Harry K. Thomas said Tuesday that the United States would provide $100,000 for disaster relief.
The rain and flooding are the result of the normal summer monsoon enhanced by the effects of Tropical Storm Haikui, the Philippines weather service said. The storm made landfall on the east coast of China on Wednesday morning.
The Philippines had already been lashed by heavy rain and wind in recent weeks resulting from Tropical Storm Saola, which plowed past it before hitting Taiwan and China at the end of last week.
The country is frequently subjected to flooding and landslides caused by heavy rain. In December, Tropical Storm Washi left more than 1,200 people dead after it set off flash floods that swept away entire villages in the southern Philippines.
CNN's Alex Zolbert in Manila, and Jethro Mullen and Anjali Tsui in Hong Kong contributed to this report.