There were no immediate reports of casualties after super typhoon Mangkhut, a category 5 storm, entered the province of Cagayan in the early hours and sent winds and rains across the entire main island of Luzon.
An average of 20 typhoons and storms lash the Philippines each year, killing hundreds of people and leaving millions in near-perpetual poverty.
Ricardo Jalad, executive director of the Philippine National Disaster Risk Reduction and Management Council, said in a statement that two rescuers who were reported Saturday to have died in a landslide in the central Philippine province of Cordillera were subsequently accounted for.
Hong Kong's weather observatory issued its highest storm warning alert - a T10 - and the normally bustling city was all but shut down as torrential rain flooded roads and buildings.
Late on Sunday, Mangkhut hit China's most populous province, bringing winds of up to 162km/h.
Reuters A view of landslide caused at the height of Typhoon Mangkhut that buried people at a mining camp in Itogon, Benguet in the Philippines, September 16, 2018.
Most shops and public services were shut, and more than 800 flights have been cancelled at Hong Kong International Airport - affecting more than 100,000 passengers.
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The official Xinhua News Agency says groceries flew off the shelves of supermarkets in the provincial capital of Guangzhou as residents stocked up in preparation for being confined at home by the typhoon.
PAGASA said Ompong maintained its strength and would gain strength as it makes landfall near Hong Kong.
The death toll in the Philippines has risen to 64, with landslides accounting for the majority of fatalities. It was located about 800 kilometers (500 miles) away in the Pacific with sustained winds of 265 kilometers (165 miles) per hour and gusts of up to 325 kph (201 mph).
Mangkhut battered the northern Philippines on Saturday before slamming into southern China on Sunday.
Officials put the number of injured at more than 200 but the territory avoided the worst of the storm.
In Hong Kong, which was hit hard over the weekend, videos on social media showed apartments swaying in the wind, scaffolding crashing to the ground and commercial buildings with windows shattered.
Around half of the more than 250,00 affected by the storm across the country sought shelter in evacuation centers in the country's north.
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