The death toll from a massive earthquake in southwest China has risen to nearly 10,000, according to state press reports.

The Xinhua news agency said the figure, which came from the disaster relief headquarters had climbed from more than 8,500.

The report came as Premier Wen Jiabao warned that rescuers faced huge obstacles reaching the area worst-hit by the quake

The quake, with a magnitude of 7.8, struck close to densely  populated areas of Sichuan province.

Thousands are feared to have been killed and injured across other areas.

There have also been reports that up to 80% of buildings in some areas collapsed during the quake,.

Xinhua has reported that up to 900 students are feared buried after a high school collapsed in Dujiangyan, a city with a population of some 600,000 people.

At least four children are confirmed dead there, and a local official said 'rows of houses' had also been demolished.

Another four children died and more than 100 were injured when two primary schools crumbled in the metropolis of Chongqing.

The Civil Affairs Ministry said that nearly four hours after the quake struck, 107 people had been confirmed dead and 34 injured in Sichuan and neighbouring Gansu and Yunnan provinces.

One of China's tallest buildings, the Jinmao Tower in Shanghai, as well as other high-rise buildings were evacuated after the quake and aftershocks. Office workers in some buildings were later allowed to return.

In February 2003 at least 94 people were killed and more than 200 injured when a quake measuring 6.8 hit the sparsely populated Jiashi county in Xinjiang.

One of the biggest quakes ever recorded was in China in 1976, which killed 242,000 people. That quake, centred in the northern city of Tangshan, lasted for 15 seconds and flattened 90% of buildings. The death toll, out of a population of 1m, made it one of the world's deadliest in the 20th century.

In 1920 and again in 1927, separate quakes in northwest China each left some 200,000 dead.