More than 420,000 houses collapsed in quake-hit Sichuan province in southwest China after two fresh aftershocks hit the area on Tuesday afternoon, state media reported.

Xinhua news agency, quoting local disaster relief headquarters, said the houses were in Qingchuan County and added 63 people had been injured there as a result, six of them critically.

Southwest China has been rocked by dozens of powerful aftershocks after an earthquake on May 12 measuring 8.0 on the Richter scale hit densely populated Sichuan province, killing at least 67,000 people.

As of noon on Monday, 182 aftershocks measuring above four on the Richter scale had been recorded in Sichuan, Xinhua said earlier, citing the China Seismological Bureau.

Tuesday's aftershocks measured 5.4 and 5.7 on the Richter scale, state media said earlier, and came within half an hour of one another.

China 'quake lake' top priority in recovery effort: state media
A swollen "quake lake" that has forced the evacuation of 150,000 people through fears of flooding is China's top priority in the ongoing earthquake relief effort, state media said early Wednesday.

Emergency workers had been aiming to move 80,000 people from their homes near the dangerously swelling lake in Beichuan county of Sichuan province by midnight (1600 GMT) on Tuesday, Xinhua news agency said.

About 70,000 people have already been evacuated.

The lake, now holding 130 million cubic metres (4.6 billion cubic feet) of water, was created when the quake triggered landslides that blocked the Jian river.

If the lake's barrier fully opens, 1.3 million people would need to be relocated, state media reported.

"The Tangjiashan quake lake should be our most urgent task," Chinese Vice Premier Hui Liangyu, who is overseeing the relief work in mountainous Sichuan province, was quoted as saying by Xinhua early Wednesday.

"It is threatening millions of lives in the area downstream and any negligence will cause new disasters to people who have already suffered the quake," he said.

Troops armed with dynamite are aiming to break up some of the new lake's banks in an effort to release some of the water in a controlled manner.

The lake is inaccessible by road and the teams of soldiers, engineers and police had to hike through remote and mountainous terrain to reach it.

Helicopters also airlifted bulldozers and other heavy machinery into the region.

The site is one of about 35 "quake lakes" that could cause huge problems if they burst, authorities have said.

The May 12 earthquake, which measured 8.0 on the Richter scale, flattened entire towns and villages across an area the size of South Korea.

The death toll from the disaster has reached 67,183, with another 20,790 people missing, a government spokesman said on Tuesday.