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The death toll of the multiple earthquakes that jolted a mountainous region in Southwest China had risen to 80, the civil affairs department of the Yunnan provincial government said on the morning of Saturday.

A car is destroyed by falling rocks in Luozehe town of Yiliang county in Southwest China's Yunnan province after an earthquake on Sept 7, 2012.[Photo/Xinhua]

Villagers affected by the earthquakes wait for assistance near a road in Zhaotong, Yunnan province, Sept 7, 2012. [Photo by Huang Xingneng/Asianewsphoto]

A farmer makes a tent in a village in earthquake-hit Zhaotong, Yunnan province, Sept 7, 2012. [Photo by Huang Xingneng/Asianewsphoto]

ZHAOTONG, Yunnan - Rescuers in Yunnan Province said on Friday night they had reached 90 percent of the six quake-hit counties under Zhaotong, where a total of 740,000 people had been affected by the quakes.

The disaster has so far incurred 3.5 billion yuan ($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 Friday, respectively.

The quakes have cut off electricity and triggered landslides that have blocked roads, creating complications for rescuers.

Yunnan's civil affairs department said the quakes destroyed 6,650 houses and damaged 430,000 others. More than 100,000 residents have been evacuated and 100,000 others are in need of relocation.

Local authorities are also taking epidemic control measures after shed collapses had killed more than 4,300 heads of cattle in Yunnan. Over 153 hectares of farmlands were damaged or destroyed.

Officials in Guizhou said two people were injured and lives of nearly 28,000 people were disrupted in Weining county. Eighteen houses were toppled and more than 10,000 houses were damaged in the quakes.

Mining community destroyed

"The hardest part of the rescue will be handling traffic," said Li Fuchun, head of Luozehe township in Yiliang. "Roads are blocked and rescuers have to climb mountains to reach hard-hit villages."

Li said the number of casualties might be high, although it will be impossible to assess until rescuers reach more remote areas.

Xinhua reporters in the hardest-hit Luozehe saw large rocks, some as tall as four meters, tumbling down mountain slopes and crushing houses and cars.

A settlement established near a zinc mine in Luozehe was seriously damaged. More than two dozen mining families were forced to evacuate.

"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.

Retired miner Liu Linde, 62, said he was thrown three meters off the road when the quake struck.

"When I returned, the door to my home had collapsed. Cracks were everywhere on the walls," Liu said.

Mass mobilization

Chinese netizens in the quake-hit region have swarmed to Sina Weibo, a popular microblogging site, to seek information on their missing family members and friends or to describe their plights after the quakes.

In one post, an Internet user in the Xiafajie Village said villagers were in desperate need of tents after their houses were damaged in the quakes.

"We dare not return to the cracked houses and had to stay in the vegetable fields. It's getting cold and we fear there might be rains," said the post by "Pig that can climb trees JY."

Chinese President Hu Jintao, who is in Russia for the Asia-Pacific Economic Cooperation (APEC) forum, has called for immediate efforts to help with disaster relief work.

In a meeting on relief work held en route to the quake zone, Premier Wen Jiabao stressed that efforts to save lives should come first to minimize casualties.

Wen also said intensified efforts will be needed to take care of the injured, as well as restore damaged infrastructure facilities to facilitate the rescue work.

Yunnan has initiated a level-one emergency response to the quakes. The Red Cross Society of China has dispatched 650 tents and 3,000 quilts to the disaster-hit region.

The Chengdu Military Area Command in southwest China said it has sent 1,300 soldiers equipped with relief materials to join rescue efforts.

Local meteorological authorities said the region will experience rains in the coming three days, which may affect the ongoing rescue. POOR BUT POPULOUS AREA

The quake-stricken area is relatively populous, which may result in heavier casualties, noted Huangfu Gang, director of Yunnan's seismological bureau.

The area's population density is estimated to be 205 people per square km, nearly twice the figure for the whole province, Huangfu said.

He said homes and buildings in the relatively poor region were not built strongly enough to resist the destructive power of a violent earthquake.

The mountainous terrain also made the quake more devastating, as landslides were more easily triggered, the expert added.

Zhaotong, with a population of about 5.6 million, is prone to geological disasters. A magnitude-5.6 earthquake in 2003 killed four people and injured 594 in Ludian county. In 2010, rain-triggered landslides left 45 dead or missing in Qiaojia county.