THE most fearsome storm the world has seen this year has claimed at least 64 lives as it tears through the Philippines, Hong Kong and Macau, leaving a trail of destruction in its wake.
Rescuers in the Philippines were desperately searching for victims of landslides, which were responsible for most of the fatalities there.
The death toll in the country reached 64 by Sunday evening and was expected to rise further, local police said, with the mudslides caused by the heavy rains still threatening communities a day after the storm hit.
Officials said at least 40 people, mostly gold miners, were feared trapped or killed by a landslide after one slope collapsed on their bunkhouses. It was not immediately clear whether the miners were accompanied by their families when they were buried.
Rescue workers at the site combed through the rocks and sludge with hand-held shovels on Sunday, pulling bodies from the debris as they went.
In Hong Kong, emergency workers began clearing trees that had fallen in major roads as terrifying videos showing super typhoon Mangkhut's destructive power emerged.
Frightening footage shows fierce winds that reached 270 kilometres per hour breaking down the doors of an international hotel, while other video shows gigantic waves beating against high rises and a crane at the top of a high rise being toppled.
More than 2.4 million people were evacuated in southern China's Guangdong province and nearly 50,000 fishing boats were called back to port, state media reported.
The storm battered mainland China on Sunday, devastating communities in its wake.
Chaos has descended on Hong Kong, where hundreds of flights have been delayed or cancelled amid "severe disruptions" at one of the world's busiest international airports.
At least 543 flights have already been scrapped in and out of Hong Kong International Airport, affecting 96,000 passengers, as authorities prepare for the onslaught of the storm.
Crazy video doing the rounds of a crane collapsing in Tai Kok Tsui as Typhoon Mangkhut hits Hong Kong. Remarkable really... pic.twitter.com/wzPYLxIuk2— Andrew Hawkins (@AndrewNJHawkins) September 16, 2018
Cathay Pacific said in a travel advisory on Saturday to expect "severe (flight) disruptions".
This video shows the doors of Hong Kong's Intercontinental Hotel being blown in by the astonishingly fierce winds.
Onlookers can be heard exclaiming: "Wow, wow!"
Mangkhut made landfall on Friday, on the northeastern tip of Luzon island in the Philippines where it collapsed houses, tore off roofs, felled trees, triggered 42 landslides and caused extensive flooding. Tens of thousands of people have been displaced by the superstorm.
Presidential adviser Francis Tolentino said an infant and a two-year-old child were among the dead. The children died with their parents after the couple refused to immediately evacuate from their high-risk community in a mountain town in Nueva Vizcaya province.
Almost all buildings in the city of Tuguegarao - the capital city of the northeastern Cagayan province - sustained damage, according to a government official. There are reports that Tuguegarao airport terminal was badly damaged, its roof and glass windows shattered by strong winds that also sent chairs, tables and papers flying inside.
Mangkhut is the most powerful storm on the planet this year with top-of-the-scale Category 5 winds, around twice the speed of the gusts generated by Hurricane Florence in the United States.
The typhoon slowed on Sunday with its maximum sustained wind speeds dropping to around 190 km/h - still powerful enough to threaten lives and property - as authorities downgraded it from a super typhoon to a "severe typhoon".
The storm left the Southeast Asian archipelago on Sunday morning and turned toward densely populated southern China and Hong Kong.
Bureau of Meteorology Australia tropical climatologist Greg Browning told news.com.au many more lives were in danger.
The Global Disaster Alert and co-ordination System (GDACS) said it expected a "high humanitarian impact based on the storm strength and the affected population in the past and forecasted path" of destruction.
As many as 43 million people could be exposed to Mangkhut's cyclonic winds, according to the GDACS.
The China Meteorological Administration on Saturday maintained its yellow alert for the approaching typhoon - the second-highest level on a four-tier scale - after warning that the region could be put to "a severe test".
On the Chinese mainland, the three southern provinces of Guangdong, Guangxi and Hainan are co-ordinating preparations, including suspending transport and moving people to shelter inland, the national meteorological agency reported. The area is home to a string of megacities and more than 100 million people. In China's Fujian province, 51,000 people were evacuated from fishing boats and around 11,000 vessels returned to port on Saturday morning
Guangdong, China's manufacturing hub, has set up 3777 shelters, while more than 100,000 residents and tourists have been moved to safety or sent home. The province has recalled more than 36,000 fishing boats to port, while train services between the cities of Zhanjiang and Maoming have been suspended and all ferry services between the Guangdong and Hainan have been put on hold.
There are fears the superstorm could affect two nuclear power plants on its projected path. Emergency officials are on standby at The Taishan Nuclear Power Plant and Yangjiang Nuclear Power Station, both in the Guangdong province.
"All emergency personnel are at their posts and have conducted their preparatory work," officials said in a statement.
In Hong Kong, Security Minister John Lee Ka-chiu urged residents to prepare for the worst as trees started to come down, waves up to 14m high smash into the banks of Victoria Harbour and locals report "random things flying in the wind".
"Because Mangkhut will bring winds and rains of extraordinary speeds, scope and severity, our preparation and response effortswill be greater than in the past," Mr Lee said.
"Each department must have a sense of crisis, make a comprehensive assessment and plan, and prepare for the worst."
The Hong Kong observatory's tracking system has hoisted the typhoon warning to a 10, the highest possible ranking. The observatory warned of rough seas and frequent heavy squalls, urging residents of the densely populated financial hub to "take suitable precautions and pay close attention to the latest information" on the storm.
Australian expat Alexis Galloway, who lives in Hong Kong, said the government has "announced on the radio they are opening 47 emergency shelters".
"There are random things flying in the wind," she told news.com.au on Saturday.
Mr Browning said Mangkhut was the most powerful storm system to have developed on Earth this year but that it wasn't the strongest since records began in 1946, as has been reported internationally. Typhoon Haiyan - which killed more than 7000 people when it lashed the Philippines with maximum sustained winds of 230km/h and gusts of 325km/h in 2013 - holds that record. Haiyan left a trail of mass destruction after it flattened villages, swept ships inland and displaced more than five million in the central Philippines.
According to Mr Browning, Mangkhut was "significantly stronger" than Hurricane Florence, which is simultaneously ripping the US state of North Carolina.
"(Mangkhut is) relatively rare (because it's) at the top of the severe scale," Mr Browning said.
"It's extremely dangerous as it's a very large system with very strong winds and a potential storm surge over a large distance.
"There will be very heavy rainfall associated with it which has potential to cause widespread damage."
On Friday, the South China Morning Post reported that the system was already stronger than any of the 15 past severe or super typhoons that warranted the highest "No 10" warning sign.
Earlier, the Joint Typhoon Warning Center in Hawaii categorised the system as a "super typhoon" which Mr Browning said equates to "very destructive winds" and heavy rainfall that's likely to cause infrastructure damage anywhere it hits.
"But the biggest killer of all with a system like this is typically the storm surge," he said.
"The region close to the typhoon's crossing can expect (to bear the brunt)."
With a 900km wide rain band - which is 50 per cent bigger than Haiyan's - combined with seasonal monsoon rains, the typhoon could also set off more landslides, according to forecasters.
Countries across east and southeast Asia have issued emergency alerts and ordered evacuations as both Mangkhut and a second storm, Typhoon Barijat taunt the region.