The measures will affect tens of millions of people and see multiple factories shut across China's manufacturing heartland.

Chinese tech hub Shenzhen has ordered the evacuation of 400,000 people, with the city's emergency management authorities warning of "severe wind, rain, waves and floods".

"Except for emergency rescue personnel and those ensuring people's livelihood, please do not go out casually," the authorities said in a statement, adding that work and market closures will begin in the afternoon.

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

"The strong winds and heavy rainfall ?the typhoon) will bring will severely impact our city, posing a critical defence situation," Foshan's emergency headquarters said in a statement.

Ragasa was generating 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, having earlier hit parts of the Philippines.

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

At least one person was killed when Ragasa lashed the northern Philippines, where more than 10,000 people were evacuated.