At least 80 people have been killed and more than 700 others injured in a series of earthquakes in southwestern China.

Tens of thousands of buildings have also been damaged.

Yesterday's shallow 5.6 magnitude quakes struck an impoverished, mountainous part of the country with poor infrastructure and telecommunications.

The death toll could rise as news trickles out of cut-off areas.

Most of the victims were from Yiliang county in Yunnan province, near the epicentre.

Footage from state broadcaster CCTV showed boulder-covered roadways, abandoned cars and black smoke billowing from buildings.

President Hu Jintao, visiting the Russian city of Vladivostok for an Asia-Pacific summit, called for efforts to help the victims and prime minister Wen Jiabao headed to the quake zone.

Rescuers in Yunnan said late they had reached 90% of the six quake-hit counties under the jurisdiction of Zhaotong city, where 740,000 people had been affected by the quakes.

Direct economic losses tallied 3.5 billion yuan, Yunnan's civil affairs department was quoted as saying.

Officials in neighbouring Guizhou said two people were injured and the lives of nearly 28,000 people were disrupted in Weining county, on the Yunnan border.