"So far 80 people have been killed and 731 others injured in the quake affected mountainous region in southwest China," state-run news agency Xinhua reported on Saturday.
Rescuers in Yunnan Province said that they had reached 90 per cent of the six quake-hit counties under Zhaotong, where a total of 740,000 people had been affected by the quake followed by a series of aftershocks.
The disaster has so far incurred USD 551 million in direct economic losses, Yunnan's civil affairs department said.
Two quakes measuring 5.7 and 5.6 on the Richter scale hit a border area near Yiliang in Yunnan and Weining county in Guizhou province at 11:19 am and 12:16 pm (local time) on Friday, respectively.
Yunnan's civil affairs department said 6,650 houses have been destroyed and 430,000 others damaged. More than 100,000 residents were evacuated and 100,000 others are in need of relocation.
Authorities are also taking epidemic control measures after shed collapses killed more than 4,300 cattle in Yunnan. Over 153 hectares of farmlands were damaged. Reports from Guizhou region said the quake destroyed an entire mining community.
"The hardest part of the rescue will be handling traffic. Roads are blocked and rescuers have to climb mountains to reach hard-hit villages," Li Fuchun, head of Luozehe township in Yiliang, said. .
Li said the number of casualties might be high, although it will be impossible to assess until rescuers reach more remote areas. Large rocks, some as tall as four metres tumbled down mountain slopes, crushing houses and cars, blocking the roads at the hardest-hit Luozehe.
"It is scary. My brother was killed by falling rocks. The aftershocks have struck again and again. We are so scared," said miner Peng Zhuwen.
President Hu Jintao and other top leaders have called for immediate efforts to help with disaster relief work.
Premier Wen Jiabao has instructed the officials to step up relief work. Wen said intensified efforts will be needed to take care of the injured, as well as restore infrastructure facilities that were damaged to facilitate the rescue work.
After withstanding the test of the 2008 Wenchuan earthquake, China is confident and capable in its ability to cope with natural disasters, he said.