A powerful typhoon slammed into southern China Tuesday, swamping ships, grounding flights and forcing thousands -- many of them still recovering from a previous storm -- to leave home.

Typhoon Kalmaegi made landfall on the east coast of Hainan island packing winds of 144 kilometres (89 miles) an hour, the China Meteorological Administration said.

More than 20,000 residents have been resettled in 24 camps in Hainan since Monday, state media said, following earlier reports which said 90,000 people were evacuated.

Kalmaegi follows Typhoon Rammasun in July, the strongest storm to hit China in four decades, which killed 62 and left swathes of devastation in the south of the country.

Survivors of Rammasun told state news agency Xinhua that while Kalmaegi appears weaker, they still feared for their livelihoods.

"Our new house has yet to be completed and we suffer again," Xinhua quoted Gao Yuanfu, who has been living in a tent since Rammasun destroyed his house, as saying.

"It is only half a month away from the harvest," he added.

Gao, from Hainan's Wengtian Township, badly injured his leg in the previous typhoon, the report said.

Images of the havoc caused by Kalmaegi showed scores of downed trees, urban streets flooded in knee-deep water and torrential rain.

More than 170 flights on Hainan were cancelled as of 9am on Tuesday, while 4,300 fishing boats in one county were called back, Xinhua said, following reports late Monday that 30,000 vessels had returned to harbour.

Rescuers in a helicopter plucked 12 Chinese sailors from a sinking cargo vessel as the storm approached the Chinese coast, Xinhua said.

But no casualties had been reported from the typhoon as of noon, the news agency added.

Local governments in China were told to prepare for "disaster-relief operations", while ferry services between Hainan and the mainland across the 30 kilometre (18 mile) Qiongzhou Strait were suspended, it said.

The China Meteorological Administration had an "orange" alert in place, the second-most severe in the nation's four-tier weather warning system.

An earlier statement, which carried the most severe "red" alert, said that up to 400 centimetres (157 inches) of rain was expected in some coastal areas.

- Hong Kong buffeted -

Kalmaegi hit China after sweeping past Hong Kong, where it disrupted flights and forced the closure of the stock market and container port.

It buffeted the city with gusts of up to 159 kilometres (98 miles) per hour as it barrelled west, injuring some 29 people, felling scores of trees and causing floods and a landslide.

The Hong Kong Observatory hoisted a number-eight cyclone warning late Monday, triggering the closure of schools and businesses. It was lowered to a number-three strong wind signal late Tuesday morning, allowing the stock market to reopen.

The storm had crossed the southern tip of Guangdong province and was over the Beibu Gulf and heading for northern Vietnam, the Observatory's website showed Tuesday afternoon.

Authorities in Hong Kong city were hauling away debris and clearing a backlog of hundreds of delayed or cancelled flights.

Television news footage showed uprooted trees, overturned bus stop signs and damaged bamboo construction scaffolding that had been torn down by the strong winds.

Typhoon Kalmaegi swept out of the Philippines on Monday after causing chest-deep floods in some rural areas but leaving the storm-prone country largely unscathed.

Six people were killed after a passenger ferry sank in the central Philippines on Saturday amid rough weather as the storm approached, the navy said.