The death toll from two earthquakes in China's western Gansu province has climbed to 89, with more than 500 people severely injured, after 1,200 buildings collapsed and tens of thousands more were badly damaged, said the official Xinhua news agency.

The quakes hit eight towns in the remote and mountainous Minxian and Zhangxian counties, about 170 km (105 miles) southeast of the provincial capital of Lanzhou, from 7:45 am on Monday (2345 GMT Sunday), Xinhua said.

The US Geological Survey reported two earthquakes, the first at a 5.9 magnitude and a strong aftershock about an hour and a half later at a 5.6 magnitude. Chinese authorities reported the first quake was a 6.6 magnitude.

Xinhua said that by Monday evening 422 aftershocks had been recorded, with the strongest measuring 5.6 in magnitude, citing Chang Zhengguo, a spokesman for the Gansu provincial government.

"Many have been injured by collapsed houses," said a Minxian county doctor surnamed Du. "Many villagers have gone to local hospitals along the roads." More than 1,200 houses had collapsed and another 21,000 severely damaged, said Xinhua.

On Monday the government of the city of Dingxi, the worst-affected area, said more than 27,000 people were left homeless.

Photos posted on Chinese social media showed roads on the sides of riverbanks had subsided and farmhouses reduced to piles of red bricks. There were also power outages and cell phone and Internet coverage was disrupted.

Xinhua said about 3,000 police and rescue personnel have been sent to the quake-hit region, though landslides and flooding have hampered their efforts, and officials said they were concerned more rain could exacerbate the need for shelter.

Gansu abuts Sichuan province, where a 6.6 quake in April killed 164 people and injured more than 6,700, China's worst quake in three years. That quake hit close to where a devastating 7.9 temblor killed some 70,000 people in May 2008. - Reuters