China on Thursday declared an emergency for parts of the country experiencing their worst drought in half a century, with some of the nation's winter harvest at risk, state media reported.

President Hu Jintao called for an all-out effort to help offset the dry spell that has spread across seven key farming provinces, leading to water shortages for millions of people and livestock.

"With the drought reaching a severity rarely seen in history, the State Flood Control and Drought Relief Headquarters has called a level two emergency," China National Radio reported.

Level two is categorised as a "serious" emergency on a four-stage scale, with level one being the worst.

Hu and Premier Wen Jiabao on Thursday ordered everything be done to secure a good summer harvest, Xinhua news agency said.

To this end, a cabinet meeting decided to earmark 300 million yuan (44 million dollars) for drought relief on top of 100 million yuan already allocated, the agency reported.

At least 3.7 million people and 1.9 million head of livestock are short of water, according to the China Daily.

About 9.5 million hectares (23.5 million acres) of farmland, representing 43 percent of the country's winter wheat supplies, are also affected, the paper said.

The situation is unlikely to improve soon as no rain has been forecast for the next 10 days, according to the China Daily.

Meteorological authorities in the central province of Henan, one of China's most populous with 93.6 million people, have called the drought the worst since 1951, after 105 days without rain.

"The severest-hit regions of Henan and (the neighbouring province of) Anhui will see their wheat harvest down by about 20 percent," Ma Wenfeng, a Beijing-based agricultural analyst, told the paper.

Further north in the capital Beijing, rain has not fallen for 100 days, a situation not seen in 38 years, the paper said.

A shortage of water, worsened by the relentless demands of a rapidly growing economy, is one of the main long-term worries for the Chinese government.