The quake hit near the city of Dingxi in Gansu province, a region of mountains, desert and pastureland with a population of 26 million. That makes it one of China's more lightly populated provinces, although the Dingxi area has a greater concentration of farms and towns with a total population of about 2.7 million.
The three deaths were reported in Min County in the rural southern part of Dingxi municipality, the Xinhua News Agency reported.
Residents described shaking windows and swinging lights but little major damage and little panic. Shaking was felt in the provincial capital of Lanzhou 177 kilometers (110 miles) north, and as far away as Xi'an, 400 kilometers (250 miles) to the east.
"You could see the chandeliers wobble and the windows vibrating and making noise, but there aren't any cracks in the walls. Shop assistants all poured out onto the streets when the shaking began," said a front desk clerk at the Wuyang Hotel in the Zhang County seat about 40 kilometers (25 miles) from the epicenter. The clerk surnamed Bao refrained from identifying herself further, as is common among ordinary Chinese.
The government's earthquake monitoring center said the initial quake at 7:45 a.m. (2345 GMT Sunday) was magnitude-6.6 and subsequent tremors included a magnitude-5.6.
The quake was shallow, which can be more destructive. The center said it struck about 20 kilometers (12.4 miles) beneath the surface, while the Gansu provincial earthquake administration said it was just 6 kilometers (3.7 miles) deep.
The U.S. Geological Survey measured the magnitude of the initial quake as 5.9 and the depth at 10 kilometers (6 miles).
Initial measurements of an earthquake can vary widely, especially if different monitoring equipment is used.
Dingxi is about 1,233 kilometers (766 miles) west of Beijing.
China's worst earthquake in recent years was a 7.9-magnitude temblor that struck the southwestern province of Sichuan in 2008, leaving 90,000 people dead or missing.
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