Ragasa churned into Guangdong, home to tens of millions of people, and AFP journalists at the impact point in the city of Yangjiang saw flying debris and gusts ripping advertisements off of buildings.

The typhoon had hours earlier swept past Hong Kong, with the densely-populated city's weather service ranking the storm the strongest yet in the northwestern Pacific this year.

Ragasa's passage in Taiwan killed at least 17 and injured 18 when a decades-old barrier lake burst in eastern Hualien county under the storm's heavy rains, according to regional officials.

Authorities earlier said 152 people were unaccounted for, but later revised that figure down to 17, saying they had made contact with more than 100 of those previously deemed missing.

More than 7,600 people were evacuated due to Ragasa and footage released by the fire agency showed flooded streets, half-submerged cars and uprooted trees.

Authorities across mainland China ordered businesses and schools to shut down in at least 10 cities across the nation's south, affecting tens of millions of people.

More than 1.89 million people across different cities in Guangdong had been relocated as of Tuesday night, its emergency management said in an online statement.

The storm made landfall along the coast of Hailing Island, near Yangjiang City around 5:00 pm (0900 GMT), Chinese meteorologists said.

Ferocious winds destroyed fences and downed trees, leaving fallen branches on the ground, AFP journalists saw.

The Yangjiang train station -- normally bustling with activity, locals said -- stood empty, with rail travel suspended Wednesday across Guangdong.

For a period of several hours, the powerful typhoon shook buildings as sheets of rain poured down on the city.

Fire trucks drove through mostly deserted streets as the winds whipped branches along the road and toppled motorbikes that had been parked along the pavement.

The weather service said that at the time of landfall, the maximum wind speed near the centre of the storm was 145 kilometres per hour (90 miles per hour).

- Hong Kong battered -

Hong Kong authorities said 90 people have been treated for injuries sustained during the typhoon period at public hospitals as of Wednesday nightfall.

More than 860 people sought refuge at the 50 temporary shelters across the city.

The Chinese finance hub recorded hundreds of fallen trees and flooding in multiple neighbourhoods. Many of the city's tall buildings swayed and rattled in the harsh winds.

At the Fullerton Ocean Park Hotel, next to a theme park, a man was seen losing his balance after a storm surge shattered the glass front doors and swept into its lobby, according to a video circulated online and verified by AFP.

A hotel spokesperson said there were no injuries.

Floodwaters rushed into the seaside Heng Fa Chuen residential estate and covered its interior courtyards, another video clip showed.

"It's like the end of the world... I never expected to see it as bad as this," said IT manager Paul Yendle near a heavily damaged restaurant in the Tseung Kwan O area, another area near the harbour.

An off-duty firefighter surnamed Tse told AFP he was "a bit worried" about the safety of nearby bamboo scaffolding as he walked home after an 11-hour shift of "non-stop" work.

Rail operator MTR said it would take time for workers to check and repair outdoor sections of train tracks.

The Airport Authority said "only a limited number of cargo flights" were scheduled for Wednesday, with its website listing hundreds of cancelled passenger flights.

A five-year-old boy and his mother fell into the sea on Tuesday afternoon while they were watching the waves in the Chai Wan district, according to police.

Both were rushed to hospital and the mother remained in critical condition on Wednesday morning.

The casino hub of Macau -- which also saw widespread flooding -- has suspended power supply to some low-lying areas, according to utility company CEM.

The typhoon trampled parts of the northern Philippines earlier this week and killed at least eight people, including seven fishermen.

Scientists warn that storms are becoming more powerful as the world warms due to the effects of human-driven climate change.