Typhoon Saomai, one of thee storms to have threatened in the last few days and which has already dumped heavy rain on Taiwan, was expected to make landfall about midway between Hong Kong and Shanghai, just south of the booming city of Wenzhou.

The province of Zhejiang had already evacuated 167,000 people and the neighbouring province of Fujian had evacuated 266,000, Xinhua news agency said, as heavy rain, strong winds and a high tide began to hit the area.

There were no immediate reports of airports closing.

Fujian authorities warned local people to prepare for Saomai, which developed from a tropical storm into a violent typhoon on Wednesday evening, gathering its power from the warm South China Sea.

"Some meteorologists said that the typhoon might grow stronger," Xinhua said.

Much of south China has been repeately battered by typhoons and tropical storms this year, with hundreds of people killed by rainstorms, mudslides and floods.

Tropical storm Bilis killed more than 600 last month and Typhoon Prapiroon killed about 80 last week.

A tropical storm fizzled to the south of Taiwan this week and another veered towards the east of Japan.

Typhoons and tropical storms are common during a season that lasts from early summer to late autumn. They gather strength over the warm water and tend to weaken once they make land.