The third highest No. 8 typhoon signal has already been raised in Hong Kong, with a higher signal expected within hours as fierce waves pounded low-lying areas and strong winds rattled windows in numerous city's towering skyscrapers.
The Philippines began evacuating thousands of people Thursday, but more than 4 million people remain at risk in Luzon, the country's agricultural center for rice and corn.
Mangkhut's peak winds have been stronger than those of Hurricane Florence, which killed five people and halted power supply to more than 900,000 USA homes and businesses in the Carolinas, before it was downgraded to a tropical storm.
China's National Meteorological Center issued an alert saying Mangkhut would make landfall somewhere on the coast in Guangdong province on Sunday afternoon or evening. The Philippines' flagship airline has canceled flights to cities in northern Luzon.
Mangkhut is the 15th - and the strongest - storm of 2018.
The dead were six people killed in landslides, a girl who drowned and a security guard crushed by a falling wall.
Concerns over massive storm surges that could be whipped inland by the typhoon's winds also prompted wardens to relocate 143 detainees from a jail in Cagayan's Aparri town.
Countries in the east and southeast Asian region have been conducting evacuations and disaster preparations in the last few days in anticipation of two powerful typhoons approaching this week. At least 128 local and global flights have been canceled, while 4,688 passengers are stranded in various seaports, the disaster risk monitoring agency said.
Meteorologists have warned that the storm may have a "high humanitarian impact" based on the high wind speeds and the exposed population located in vulnerable areas.
Mangkhut struck Cagayan province in the northern Philippines on Saturday with winds of up to 269km an hour, leaving at least eight dead and sending about 206,000 people to shelters, according to data from various agencies. "We are preparing our emergency assets and relief items".
Now a tropical storm, Florence spreads watery mayhem across Carolina
More than 10 million people are under hurricane watches or warnings and 1.7 million have been ordered to evacuate the coast. Zooming out to the full projection, shown above, the core of the storm is slated to enter North Carolina around 2 p.m.
Almost 37 million people are estimated to be in the storm's path, according to the Global Disaster Alert and Coordination System.
"It's something that we are not used to", Robil said.
Farmers are rushing to bring in their rice harvests ahead of Mangkhut, ABS-CBN reported.
"The typhoon is already devastating homes, business and overall livelihood", Ortega-Anderson said.
Mangkhut slammed ashore before dawn Saturday in Cagayan province in the northeast and is on target to hit southern China on Sunday.
Officials in Hong Kong held emergency meetings Wednesday in which all departments were warned to have "their deployment and emergency response plans ready for the possible threats".
The worst of the storm will be borne by Hong Kong and Macau, however, which are now in Mangkhut's path. Authorities were also checking what happened to about 70 men who reportedly returned to their coastal village to check on their homes during unsafe storm surges that saw walls of seawater whipped inland. Lorenzana also said troops were available in Cagayan and other affected provinces for rescue missions.
After the Philippines, the Hong Kong Observatory predicts Mangkhut will plow into the Chinese mainland early Monday south of Hong Kong and north of the island province of Hainan.
In nearby Fujian province in China, 51,000 people were evacuated from fishing boats and around 11,000 vessels returned to port on Saturday morning.
Cathay Pacific Airways Ltd. said in a statement it's cancelling all flights in and out of Hong Kong on Sunday beginning at 2:30 am, and wouldn't resume operations until 4 am the following day.