Police in the Philippines say at least 40 people, mostly gold miners, are feared trapped in a landslide in the north of the country.
This comes a day after the biggest storm of the year left at least 28 dead from landslides and drownings in the northern Philippines.
Hong Kong and southern China are on red alert as strong winds of 100 mph and heavy rain from Typhoon Mangkhut hit the densely populated coast.
Nearly half a million people had been evacuated from seven cities in Guangdong province, the gambling enclave of Macau closed down casinos for the first time and the Hong Kong Observatory warned people to stay away from the Victoria Harbour landmark, where storm surges battered the waterfront reinforced with sandbags.
Mangkhut made landfall in the city of Taishan in Guangdong province at 5pm local time, with wind speeds of 100 miles per hour. State television broadcaster CGTN reported that surging waves flooded a seaside hotel in the city of Shenzhen.
The Hong Kong Observatory said although Mangkhut had weakened slightly, its extensive, intense rainbands were bringing heavy downfall and frequent squalls.
Hundreds of flights were cancelled. All high-speed and some normal rail services in Guangdong and Hainan provinces were also halted on Sunday, the China Railway Guangzhou Group Co said.
In Fujian province and elsewhere, tens of thousands of fishing boats returned to port and construction work came to a stop.
Philippine National Police Director General Oscar Albayalde said that 20 people had died in the Cordillera mountain region, four in nearby Nueva Vizcaya province and another outside of the two regions.
Three more deaths have been reported in north-eastern Cagayan province, where the typhoon made landfall before dawn on Saturday.
Among the fatalities were an infant and a two-year-old child who died with their parents after the couple refused to immediately evacuate from their high-risk community in a Nueva Vizcaya mountain town, said Francis Tolentino, an adviser to Philippine President Rodrigo Duterte.
“They can’t decide for themselves where to go,” he said of the children, expressing frustration that the tragedy was not prevented.
Mr Tolentino, who was assigned by Mr Duterte to help coordinate disaster response, said at least two other people were missing.
Mayor Mauricio Domogan said at least three people died and six others were missing in his mountain city of Baguio after strong winds and rain destroyed several houses and set off landslides, which also blocked roads to the popular holiday destination.
It was not immediately clear whether the dead and missing had been included in the overall death toll.
About 87,000 people had evacuated from high-risk areas of the Philippines. Mr Tolentino and other officials advised them not to return home until the lingering danger had passed.