A "super typhoon" has struck the northern Philippines with heavy rain and winds of up to 260km/h (162mph), leaving at least three people dead.
Typhoon Megi made landfall in Isabela province at 1125 local time (0325 GMT), destroying buildings and crops, cutting power and telecommunications.
Thousands sheltered in public buildings or fled to higher ground, and a "state of calamity" was declared in Isabela.
The category-five storm is forecast next to head towards China and Vietnam.
More than a dozen people are already missing in central Vietnam after floodwaters swept away a bus. At least 20 others are known to have been killed in floods as heavy rain pounded the region.
On the southern Chinese island of Hainan, the rain prompted more than a 100,000 people to leave their homes over the weekend.
With sustained winds of 225km/h (140mph) and gusts of up to 260km/h, Megi was the strongest storm the Philippines has faced since 2006, when 1,000 people were killed by mudslides triggered by Typhoon Durian.
Shortly before midday on Monday, Megi made landfall at Palanan Bay on the main northern island of Luzon, whipping up huge waves - forecasters had said they might be greater than 14m (46ft).
Local media said the rain meant there was near-zero visibility and that the wind was so powerful people could barely walk outside. Ships were told to stay in port, and domestic and international flights were cancelled.
More than 4,150 people took shelter in school buildings, town halls and churches as the typhoon blew over Isabella, officials said. Many others fled to higher ground after warnings of flash floods and landslides.
Television footage showed uprooted trees lying on roads, and metal and thatched roofing blown off houses. Up to 90% of communications in Isabela and Cagayan provinces might have been knocked out, officials said.
"We are marooned inside our home. We cannot go out. The winds and rain are very strong. Many trees are being uprooted or snapped in half," Ernesto Macadangdang, of Burgos, Isabela, told local radio.
Despite the destruction, only three people have so far been reported killed.
One man who had just rescued his water buffalo slipped and fell into a river and drowned in Cagayan province. A woman was killed when a tree crushed her house and injured her child in Kalinga province, and a security guard died after being struck by a tree in Baguio, in Benguet province.
At a news conference in Manila, the director of the national disaster agency expressed sadness over the deaths.
"The governor of Isabela declared a state of calamity, so there could be massive damage and destruction there," Benito Ramos said.
"Power has been cut and crops about to be harvested could have been destroyed. We have no actual report because we're waiting for the weather to clear up to make an assessment."
Thousands of military reservists and volunteers are on standby to assist those affected, along with several helicopters, Mr Ramos added. Trucks, rescue boats and food packs were also pre-positioned near vulnerable areas.
Farmers were urged to harvest as much of their crops as possible before the typhoon hit, the BBC's Kate McGeown in Manila. The area in the storm's path was one of the country's main rice-growing regions.
Correspondents say the Philippines is the world's biggest rice importer, and damage from the typhoon could see it buy more than had been expected for 2011, which could push up international prices.
In July, President Benigno Aquino sacked the head of the weather bureau after he failed to predict a typhoon which unexpectedly changed course and hit Manila and its outlying provinces, killing more than 100 people.