The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) issued a red alert signal for the metropolitan region of Manila, the capital, warning of serious flooding in the urban heart of the Philippines.
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.
Video from CNN affiliate ABS-CBN showed fast-flowing torrents of water carrying debris past submerged houses in the Manila region. People up to their necks in the water scrambled to get out.
Police officers and army reservists have been mobilized to help with rescue efforts, the network reported.
Local officials were urging residents to move to higher ground from affected neighborhoods. The authorities in Marikina City imposed a forced evacuation of areas near the Marikina River, which has risen above critical levels, the state-run Philippines News Agency (PNA) reported.
The dam on the La Mesa Reservoir near Quezon City began overflowing on Monday night, sending more water toward low-lying areas, the National Disaster Risk Reduction and Management Council said.
The rain and floods prompted the Philippine Stock Exchange to close Tuesday and the Philippine National Railways to suspend its provincial and commuter services, according to the PNA.
The heavy monsoon rains have inundated the island of Luzon, where Manila is situated. The downpours are expected to continue into Wednesday, PAGASA said, warning that landslides and flash floods were likely in mountainous areas.
The effects of the monsoon are being exacerbated by Typhoon Haikui, which is moving toward the eastern coast of China, hundreds of kilometers to the north.
Besides the Manila region, which is home to nearly 12 million people, severe flooding was being reported in other areas of Luzon, the largest island in the Philippines. Nearly 19,000 people displaced by the rain and floods were staying in evacuation centers as of Tuesday, the national disaster council said.
The Philippines had already been lashed by heavy rain and wind in recent weeks resulting from Tropical Storm Saola, which plowed past the country before hitting Taiwan and China at the end of last week. The combination of Saola and monsoon rains had left a total of 53 people dead in the Philippines by Tuesday morning, according to the disaster council.
Infrastructure is poor and poverty is widespread in the Philippines. Many people live in crowded neighborhoods full of badly constructed houses.
The country is frequently the victim of 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.
