Water levels have risen to critical levels along vast Chinese rivers and floods have spread to the north while a tornado hammered 33 villages in the east and two central provinces suffered drought, media said on Thursday.

A paramilitary policeman rescues a man trapped during a flood in Guang'an, southwest China's Sichuan province, earlier this month. Summer floods have killed more than 500 people and displaced hundreds of thousands. [Reuters]

More than 500 people have been killed since the summer floods started, but the disaster has failed to gain world attention surrounding floods in England in which three deaths have been reported.

Four people died in the normally arid northwestern province of Gansu and the neighbouring frontier region of Xinjiang this week, Xinhua news agency said.

Two farmers in Xinjiang's Huocheng county were swept away by flood water triggered by heavy rain that started on Tuesday, Xinhua said.

"At least 48 herdsmen and 13,000 goats have been stranded for nearly two days in a mountainous area in northwestern Xinjiang after a landslide cut off their path," it said.

On Wednesday, a tornado swept across a six-mile path through 33 villages in Yinshang county in the dirt-poor eastern province of Anhui.

The villages were the among worst hit during weeks of serious flooding along the swollen Huai River, which has displaced hundreds of thousands of residents, Xinhua said.

"It is like adding frost to the snow," it said.

State television showed pictures of uprooted trees, downed electricity poles and houses without roofs by the tornado.

Nearly 100,000 trees were uprooted or severed and large areas of crops were destroyed, causing economic losses of $2.9 million, the China Youth Daily said.

There have been no reports of casualties from the tornado, which hit in the early morning, but water levels along the Huai remained at alarming levels.

In the southwestern province of Guizhou, at least one person died and 645,000 people were affected by rainstorms this week, Xinhua said.

Water levels of two rivers in the scenic Xiangxi area in the central province of Hunan rose to up to seven metres above danger levels after days of heavy rain, prompting dams to open flood gates, the official news agency said.

About 26,000 people in central Hubei have been mobilized to check embankments as flood peaks on the Yangtze River, China's longest, and its main tributary the Han River, approached the provincial capital, Wuhan.

More rain is forecast for large swathes of southwest and northwest China on Thursday, the National Meteorological Centre reported on its website.

Weeks of high temperatures were set to continue in the south and southeast. Temperatures in the eastern provinces of Zhejiang and Jiangxi could hit 104¡ãF, the center said.

And more than 300,000 people in the central province of Jiangxi and about half a million in neighbouring Hunan faced a shortage of drinking water because of drought, Xinhua said.

The temperature in the financial hub, Shanghai, reached 100¡ãF on Wednesday and some office workers had been urged to wear shorts and T-shirts on Friday to save energy.