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) on Saturday, the State Seismological Bureau said.
Eight of the 25 people were seriously wounded while the others suffered minor injuries.
The People's Daily website, however, said 29 people were injured and four others buried in rubble had not been rescued.
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.
A Chinese news agency, citing the ministry of civil affairs, said more than 10,000 residential rooms had been destroyed by the quakes.
Sources from the Gansu provincial seismological bureau said 30% of the houses in the epicenters had been severely damaged, while 90% of the buildings in one village, Yaozhaizi, had collapsed.
Cold weather in the disaster-hit areas are adding to the problems of quake victims.
Temperatures in the area dropped five to six degrees below zero Celsius (23 degrees to 21 degrees Fahrenheit) and it had snowed in the area a few days ago.
The ministry has sent 2000 cotton-padded tents to quake-hit regions.
Zhangye's mayor, Tian Baozhong, said many officials, locally-based 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 quake damaged a reservoir in Mingle county, which stored 20 million cubic meters of water, the Daily quoted another official as saying.
After cracks were found in the reservoir's gate, officials began slowly releasing water as they tried to repair the structure to prevent a major accident.
The epicenters of the quakes are about 500km from Lanzhou, the capital of Gansu province.
The provincial government and the State Seismological Bureau have sent a task force to the area, the report said.
Chinese Premier, Wen Jiabao, has asked the ministry to respond in a quick and comprehensive manner to help the victims.