He said tens of thousands of troops were reinforcing and raising embankments around the provincial capital Harbin.

Soldiers using water pails to tackle flood water in Harbin city

The city, at the edge of the river, has a population of about nine million and is home to some of China's biggest industrial concerns.

Latest reports say a flood crest on the Songhua River is expected to surge through the city on Friday adding to water levels already at an all time high.

Officials say they may use a specially built flood diversion zone to lower the level of the river if necessary.

Army helicopters aid evacuation of stranded flood victims

To the south, flood waters on both the Yangtze and Han Rivers are putting what state television called "special pressure" on embankments close to the city of Wuhan.

Further north the railway line linking Harbin to Daqing, China's biggest oilfield, has been cut, according to the China Daily newspaper.

Flood waters in north-east China overwhelmed a dyke protecting the country's largest oilfield and almost 2,000 of Daqing's wells have been affected. Most are still functioning, however, protected by a hastily built flood barrier.

Millions are already homeless

The China Daily newspaper reports 100,000 people will have to be relocated.

The paper said the continuing crisis had bound the nation together, adding that the floods might break embankments but not what it called "the great wall of our will".

Donations to flood relief efforts now total more than $190m.

One survey said three quarters of Shanghai residents were donating money, while an article in the Beijing Daily said many residents in the city had given up watching soap operas to concentrate on the latest reports from the flood front line.