The quake shook the area at 7:45 a.M. (local time) at the junction of the Minxian County and Zhangxian County, the Gansu Provincial Seismological Bureau said.
The epicenter, with a depth of 20 km, was 170 km away from the provincial capital Lanzhou, state-run Xinhua news agency quoted officials as saying.
A 5.6-magnitude quake jolted the same area later at 9:12 a.M, the agency said.
"The death toll from the deadly quake has risen to 47, with 296 injured," Xinhua quoted Gansu Earthquake Networks Center as saying.
More From This Section
Communication was cut off in 13 towns of Zhangxian County. Officials of with the Minxian County government said most of the townships in the county have been affected by the quake. The townships of Meichuan and Puma were seriously hit.
Many homes in the quake-hit region collapsed, according to the civil affairs bureau of the Dingxi City.
The locals in Minxian County said strong tremor was felt in the area and they saw trees and homes were shaking. They also said that the quake lasted for about one minute.
The Red Cross Society of China has also dispatched a team of disaster relief workers, with 200 tents, 1,000 family emergency kits and 2,000 cotton-padded jackets.
Lanzhou Railway Bureau has started the emergency response to guarantee the safety of railway bridges and communication equipment in the province.
Light to moderate rain and partly heavy rain were forecast in Dingxi city, according to the provincial meteorological station, which would affect the rescue efforts.