The Philippines was just beginning to count the cost of the typhoon, but police confirmed at least 49 are dead - including a baby and a toddler - after Mangkhut struck northern Luzon on Saturday.
At least two people were killed in Guangdong province and 2.4 million people were evacuated. A 40,000-ton-category vessel with 73 people on board was blown off its anchoring at Huizhou port this morning, China's Central Television reported.
In China, meanwhile, Mangkhut continued its destructive path, with Hong Kong bracing for a storm that could be the strongest to hit the city since Typhoon York in 1999. Hong Kong lowered typhoon signal to No. 8, which will remain in force "for a period of time". The densely populated city turned into a ghost town as residents shut themselves indoors after emptying the shelves of supermarkets.
Mangkhut will keep to a northwesterly track, bringing heavy rain and winds when it enters the autonomous region of Guangxi early on Monday, before weakening into a tropical depression as it arrives in southwestern Yunnan on Tuesday.
Authorities also were were verifying the drownings of three people, including two children who reportedly died as the typhoon approached. Macau reported seven injuries and suspended all casino operations.
Netizens in Hong Kong and mainland China have taken to social media to post videos of the widespread destruction caused by winds of more than 250kmh and waves over 12m high. Fallen trees forced closures of roads and a tunnel.
Hong Kong's home affairs department said it had opened 48 temporary shelters and was now housing more than 1,200 people displaced by the storm.
They opened again on Monday but Macau was still in recovery mode after severe flooding hit parts of the city, forcing emergency workers to rescue people from their shops and homes using boats and jetskis.
Hong Kong flag carrier Cathay Pacific Airways Ltd (國泰航空) said all of its flights would be canceled between 2:30am yesterday and 4am today. Underground trains are running at reduced intervals with stations largely empty.More news: MA officials briefing on gas explosion latest
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The Hainan provincial tourist department has ordered all scenic areas, schools and outdoor businesses to close on Sunday and Monday morning.
A storm surge of about 9.8 feet or above is expected at the city's waterfront Victoria Harbour, the observatory said, appealing on the public to avoid the shoreline. "Prepare for the worst", Hong Kong security minister John Lee Ka-chiu urged residents. In China, power disruptions affecting 168,700 users in Guangdong, with 81,900 people still without normal power, Xinhua News Agency reported.
It has already left about 60 people dead in the Philippines when it passed through the day before.
President Rodrigo Duterte appeared at a televised Cabinet meeting following an aerial inspection of the affected areas and pledged funds following an for the recovery.
Guangdong is also China's most populous province, with a population of more than 100 million.
"There are still areas without power and a lot of areas with evacuees".
Impacts of the storm were felt as far away as Taiwan, where high waves caused one death, according to the island's government. Winds there reportedly reached more than 110 miles per hour (117 kph).
Economic losses in Hong Kong and across China could reach $50 billion on top of the $16 billion to $20 billion it probably exacted in the Philippines, said Chuck Watson, a disaster modeler for Enki Research in Savannah, Georgia.