More than 30,000 trapped by floods

More than 30,000 people are thought to be trapped by floodwaters in a town in northeast China.

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MORE than 30,000 people are thought to be trapped by floodwaters in a town in northeast China, state media said on Wednesday, as torrential rain that has killed at least 300 in a fortnight continues.

China is struggling with its worst floods in a decade that have caused at least $US22 billion ($A24.4 billion) in damage, and authorities have warned of more to come.

In the central city of Wuhan, tens of thousands of people have been evacuated as authorities brace for flood crests from the Yangtze River and one of its tributaries to converge there.

More than 200 rescue workers have been sent to northeastern Jilin province's Kouqian town to reach 30,000 residents thought to be trapped after a nearby reservoir overflowed, Xinhua news agency said.

The local train station was also surrounded by water with more than 80 people trapped inside, it said.

Factories and houses have been submerged by floods that have reached highs of three metres in some places and residents are trying to escape to higher buildings, the official China News Service reported.

Jilin is the latest province to have been hit by recent deadly floods that have killed 333 people since July 14 and left a further 300 missing, according to the latest official figures.

Since the beginning of the year, flooding has left 1260 dead or missing.

Until now, torrential rains have mostly hit China's south, swelling the Yangtze - the nation's longest waterway - and some of its tributaries to dangerous levels.

Engineers at the Three Gorges Dam on the Yangtze have already coped with two flood crests, but both passed largely without incident as the dam's massive spillgates released torrents of water.

But authorities are now worried about Wuhan, capital of Hubei province, which is downstream from the dam. Flood peaks from the Yangtze and its tributary the Han River are set to converge there.

Thousands of soldiers and emergency workers are laying down sand bags along the rivers in the city of nine million, a transport and economic hub.

In the nearby city of Xiantao, workers are on standby to open flood gates and divert water from the Han to a walled low-lying area covering 450 square kilometres.