The powerful storm posed a wide threat to lives and homes, prompting authorities in mainland China to order businesses and schools to shutdown in at least 10 cities across the nation's south.

Ragasa had already toppled trees, tore the roofs off buildings and killed at least one person in a landslide while lashing the northern Philippines, where thousands sought shelter in schools and evacuation centres.

The super typhoon was a very dangerous storm as it moved west, packing maximum sustained winds of 230 kilometres (140 miles) per hour at its centre while churning across the South China Sea, according to Hong Kong's weather service.

The city of 7.5 million was preparing for the extensive disruption and possible damage, while nearby Chinese tech hub Shenzhen has ordered the evacuation of 400,000 people.

"Ragasa will pose a serious threat to Hong Kong, which could reach the levels of Hato in 2017 and Mangkhut in 2018," Hong Kong's number-two official Eric Chan said on Monday -- referring to two super typhoons that each cost hundreds of millions in property damage.

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

Hong Kong's airport will remain open but there will be "significant disruption to flight operations" from 1000 GMT Tuesday until the next day, the Airport Authority said.

More than 500 Cathay Pacific flights are expected to be cancelled.

Hong Kong Observatory said it would issue its third-highest typhoon warning, T8, at 0620 GMT on Tuesday, at which point businesses close up and most transport shuts down.

Emergency management authorities in Shenzhen said that except for emergency rescue personnel and those ensuring people's livelihood, "do not go out casually".

Other cities in the Southern province of Guangdong that are implementing the suspension measures include Chaozhou, Zhuhai, Dongguan and Foshan.

- 'Better precautions' -

Residents crowded into markets and grocery stores to stock up ahead of Ragasa's arrival.

"There's bound to be some concern," said supermarket shopper Zhu Yifan, a 22-year-old student from China.

Zoe Chan, in her 50s, piled up sandbags outside her clothes shop in the Wanchai district of Hong Kong, saying she expected her business to be "ruined" by water damage.

"The most important thing is to take better precautions, so I can rest easier," Chan told AFP.

Classes were to be suspended on Tuesday and Wednesday, while the Hong Kong Jockey Club also cancelled Wednesday's horse-racing meet.

Hong Kong's stock exchange changed its rules this year to keep markets open during typhoons, with the operator telling Bloomberg News that it was "closely monitoring" the situation.

Authorities have told residents of low-lying areas to be alert to flooding, while opening 46 temporary shelters.

Ragasa -- named after the Filipino word for rapid motion -- will be closest to Hong Kong and nearby casino hub Macau on Wednesday morning, according to Chinese weather services.

People in southern mainland China were also rushing to make preparations ahead of the storm.

Shelves of fresh meat and vegetables were mostly bare at a supermarket in Shenzhen's Bao'an District on Monday evening, AFP journalists saw.

Checkout queues were long in the bustling store as people hurried around to pick up supplies.

A supermarket employee told AFP that bread had already sold out by midday, adding, "It's not normally like this."

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