At least 64 people were killed and 550 injured when two quakes struck a remote and mountainous area of southwest China on Friday, toppling buildings and pushing panicked crowds into the streets, officials and observers said.
Residents described how people ran out of buildings screaming as the two quakes hit on the border of southwestern Yunnan and Guizhou provinces an hour apart around the middle of the day followed by a string of aftershocks.
Television footage showed people running from damaged buildings and streets strewn with fallen bricks and rocks in Yunnan province's Yiliang district, which appeared to be worst hit.
The Xinhua news agency said 64 people had been killed and rescuers have rushed to the area. Authorities are sending thousands of tents, quilts and coats, and Prime Minister Wen Jiabao is also heading to the area, it said.
The Yiliang county government said on its website that 556 people had been injured, while an online statement from the public affairs bureau in Zhaotong city, which overseas Yiliang, put the figure at 150.
The Zhaotong statement also said 100,000 people were made homeless by the disaster, and at least 20,000 houses collapsed or were damaged.
Altogether 700,000 people have been affected, it said.
The death toll could still rise as some villages remain blocked by landslides and the worst-hit areas may have lost power and communications, Xinhua said, citing local officials.
"The hardest part of the rescue now is traffic," Li Fuchun, the head Luozehe township, identified as the epicentre, was quoted as saying. "Roads are blocked and rescuers have to climb mountains to reach hard-hit villagers."
Rocks as tall as four meters (13 feet) crashed into mountain roads and landslides were also triggered, the report said.
The death toll may have been higher because of the area's denser population, with 205 people per square kilometer compared to 117 across the province, said Huang Pugang, head of the Yunnan seismological bureau, according to Xinhua.
In addition the epicentres of both major quakes were located just five to 15 kilometres from the county seat, he said, while the homes and buildings in the poor area might not have been built to withstand strong quakes.
Footage broadcast on state television network CCTV showed hundreds of people crowded into a sports field in Yiliang, a sprawling town surrounded by green mountains.
Many people took cover outside after the first quake and did not return indoors, said a man surnamed Xia reached by phone. "Lots of people are outside because they fear aftershocks," he said.
"I was walking on the street when I suddenly felt the ground shaking beneath me," posted one witness on Sina Weibo, a microblog similar to Twitter. "People started rushing outside screaming, it still scares me to think of it now."
So far, no casualties have been reported in Guizhou province, but the quake has damaged 1,540 homes there, Xinhua said, quoting the provincial civil affairs department.
The US Geological Survey said the first quake struck at 11.20 am (0320 GMT) at a depth of around 10 kilometres (six miles), with a second quake around an hour later, putting the magnitude of both at 5.6.
The China Earthquake Networks Centre put its magnitude at 5.7 and said it struck at a depth of 14 kilometres.
Southwest China is prone to earthquakes. In May 2008, an 8.0-magnitude quake rocked Sichuan and parts of neighbouring Shaanxi and Gansu provinces, killing tens of thousands and flattening swathes of the province.
Yiliang county has a population of 550,900, according to the latest official figures, and is listed as a priority district for state aid due to its poor infrastructure and the low average income of residents.
Local hospitals and government officials could not be reached for comment.