Super Typhoon Yagi slammed into southern China's Hainan island on Friday, bringing windspeeds of over 230 kilometers (143 miles) an hour in what is set to be the strongest storm to hit the region in over a decade.
Hainan province evacuated over 400,000 people ahead of the storm's expected landfall, while tens of thousands prepared to seek shelter in neighboring Vietnam.
Yagi killed at least 13 people in the Philippines earlier this week when it was still classified as a tropical storm, triggering floods and landslides on the country's main island of Luzon before strengthening into a super typhoon over the past few days.
The storm made landfall in China on Friday along the coast of Hainan -- a popular holiday destination -- and neighboring Guangdong province, at 4:20 pm local time (0820 GMT), the state-run Xinhua news agency said, citing authorities.
The typhoon "is equivalent to a Category 4 hurricane", according to NASA Earth Data.
In Hong Kong, a typhoon warning that had been in effect was lowered shortly after noon following heavy rains overnight as Yagi passed within 400 kilometers of the city.
Trading at Hong Kong's stock exchange was suspended on Friday, and day schools were closed.
Authorities said five people were injured in the city due to the weather, but damage was limited.
Southern China is frequently hit during the summer and autumn by typhoons that form in the warm oceans east of the Philippines and then travel west.
But climate change has made tropical storms more unpredictable while increasing their intensity -- leading to heavy rains and violent gusts that cause flash floods and coastal damage, experts say.
After moving through southern China, Yagi will head towards Vietnam, on course to hit the northern and north-central regions around the famed UNESCO heritage site Halong Bay on Saturday.
Tens of thousands of people will be evacuated to safer areas in Hai Phong and Thai Binh provinces on Friday, local authorities said.
"This will be the strongest typhoon (to hit northern Vietnam) in 20 years," said Pham Duc Luan, head of the dyke management authority on Thursday.
More than 457,000 military personnel have been mobilised by the relief and rescue department of the defence ministry.
Officials have also directed 50,000 fishing vessels carrying 220,000 people to take shelter.