Most of the damaged crops was rice, officials said. State media has estimated that the drought, which has also hit neighbouring Chongqing, has cost farmers more than US$1 billion. It has not said whether there have been any deaths.

More than half Sichuan's counties were drought-stricken and almost 10 million people had restricted access to drinking water, the newspaper said.

It quoted a scientist as saying that a gas leak in March in Chongqing that forced the evacuation of 5,000 people could have intensified the drought, as methane caused a mini-greenhouse effect, raising temperatures.

But another scientist said it was purely a weather-related drought and had nothing to do with methane.

This week, an agricultural official told Reuters the drought had helped push up prices for vegetables, poultry and pork, though it had yet to affect grain.

The drought has been so severe that the government is helping 100,000 farmers move to the far-western region of Xinjiang to pick cotton after their own fields withered.

And the dry weather is causing water levels in China's largest freshwater lake, the Poyang, in southeastern Jiangxi province, to fall as it is fed by the Yangtze which flows through Sichuan.

Grain analysts say the total rice harvest this year is likely to grow from last year's 180 million tonnes because of acreage expansion in the northeast.

"Northeast provinces have increased their rice acreage by a big margin, which can offset the losses," said one analyst at the China National Grains and Oils Information Centre.