The death toll climbed from four to nine as victims buried under collapsed buildings were found Sunday, the ministry of civil affairs and State Seismological Bureau were quoted by the Xinhua news agency as saying.

The quakes, measuring 6.1 and 5.8 on the Richter scale, jolted areas between Minle and Shandan counties of Gansu province's Zhangye city at 8:41 pm (1241 GMT) and 8:48 pm (1248 GMT) Saturday, the Bureau said.

Six of those injured were in a serious condition while another 37 suffered light injuries, Xinhua said.

But an official told AFP the final tally was not yet available.

"Approximately four townships have been affected. I don't know exactly how many people have suffered," said the official from the Zhangye city seismological bureau.

Most residents in the area are farmers or herdsmen.

More than 10,800 residential rooms were destroyed by the quakes and more than 3,000 livestock were killed or hurt, Xinhua said, citing the ministry. China usually records property damage in terms of rooms rather than buildings.

Sources from the Gansu provincial seismological bureau said 30 percent of the houses at the epicenter of the quakes had been severely damaged. Around 90 percent of the buildings in one village, Yaozhaizi, had collapsed, Xinhua said.

Damage was also caused to schools, grain warehouses, bridges, water and power supplies.

By 12:30 pm Sunday, 170 aftershocks measuring above 0.5 on the Richter scale had occurred.

Cold weather in the disaster-hit areas were adding to the problems of quake victims. Temperatures in the area dropped to minus five-six degrees Celsius (23-21 degrees Fahrenheit) and it had snowed in the area a few days ago, Xinhua said.

The ministry has sent 2,000 padded tents to quake-hit regions.

Zhangye's mayor Tian Baozhong said officials, People's Liberation Army soldiers and the armed police were searching for injured people while trying to recover food from collapsed homes, according to the People's Daily.

The quakes also damaged the dams of two reservoirs in Mingle county, prompting officials to slowly release water as they tried to repair the structures to prevent a major accident.

Chinese Premier Wen Jiabao has asked the ministry to respond in a quick and comprehensive manner to help the victims, Xinhua said.

The two quake-hit counties are both located on an earthquake-prone belt in northwest China, along the Qinlin mountain faults, which have long been the culprit of some of the deadlest quakes in the early 20th century in China, according to Xinhua.

In 1920, a deadly quake measuring 8.5 on the Richter scale struck Haiyuan county and neighboring counties, killing 200,000 people.

A powerful quake measuring 7.25 on the Richter scale struck Shandan county in 1954, claiming 50 lives and injuring more than 300.

TERRA.WIRE