MANILA, Philippines — (UPDATE) At least 50 people were reported dead as tropical storm “Ondoy” (international code name: Ketsana) lashed the Philippines, bringing massive flooding, television and radio reports said early Sunday.

At least 40 were killed in Rizal province, east of Manila, as entire towns were inundated, Rizal Governor Casimiro Ynares was quoted as saying by GMA television.

Radio stations had earlier reported 10 dead in Manila and its surrounding areas. This included a father and child killed by a collapsing wall weakened by the flood as well as others swept away by rising waters.

Ynares said there were many more missing in flooded towns in his province but he did not give details.

The government declared Manila and 25 other provinces to be in a "state of calamity," Defense Secretary Gilberto Teodoro said, as heavy rains brought by the storm caused the worst flooding in the capital in some 20 years.

Amid a rash of cellphone calls for help by people stranded on the roofs of their houses, President Gloria Macapagal-Arroyo appealed to the public to stay calm and follow the instructions of local officials and civil defense workers.

Over 1,800 people were forced to flee their homes and take refuge in evacuation centers due to rising waters, the Office of Civil Defense said.

Flooding was reported in many districts with waters in some areas reaching as high as the rooftops of one-storey buildings, it added.

Power was cut in many areas of Manila, partly due to flooding but also as a protective measure to prevent fallen lines electrocuting people trying to escape the waters.

Defense Secretary Teodoro, who is also in charge of civil defense operations, said all the efforts of the police and the military were being concentrated on rescuing people trapped on rooftops.

But he said the flooding in the streets and the large numbers of stalled vehicles were giving rescue units "a hard time" in reaching those affected.

In a radio broadcast, he advised that "if you are on the roof, don't try to leave. Just remain there on the roof and we will do everything to rescue you."

He remarked that even he had to swim through chest-deep waters to reach his office.

The storm, bearing winds of 85 kilometers (53 miles) per hour with gusts of 100 kph, hit the main island of Luzon near the town of Infanta at about 0200 GMT Saturday, moving west at 19 kph, the weather station said.

Government weather forecaster Gener Quitlong said the equivalent of one month's worth of rain fell on Manila in less than a day.

"We knew there would be rain but not like this," Quitlong told reporters.

One of the three airport terminals in Manila was forced to cancel and divert flights after the flooding hampered its electrical system.

Local officials interviewed on radio said they were moving to evacuate more of their residents.

At least four hospitals in the capital had to move their patients to higher floors after water began seeping into lower levels.

The highways leading to metropolitan Manila were rendered impassable due to the huge number of vehicles stalled in the floodwaters.

Local officials made radio appeals asking rescue agencies to send rubber boats to rescue stranded people, some of whom had been on their rooftops all day and were panicking because of rising waters.

In a suburb of Manila, residents in a flooded area were seen rescuing children from rooftops by placing them in inflated inner tubes before dragging them to higher ground.

The second level of a three-step storm alert was raised over the eastern provinces of Luzon while the first level alert was hoisted over metropolitan Manila and surrounding areas, the government said.

The storm is expected to move west, across the main island of Luzon, before leaving the country early Sunday. The government weather station said it is weakening and that rains are likely to ease.

An average of 20 typhoons and storms hit the Philippines every year.