A magnitude-6.6 earthquake killed at least 75 people, injured more than 600 and left 14 others missing Monday in the northwestern Chinese province of Gansu, officials said.

The temblor occurred around 7:45 a.m. between Minxian and Zhangxian districts, an area that was affected by torrential rains recently, the Chinese Seismology Monitoring Center said.

The majority of the province's cities have been affected by the earthquake, with towns cut off from communications networks by power outages, officials said.

The quake's epicenter was in Dingxi, a city of nearly 2.7 million located about 170 kilometers (105 miles) east of Lanzhou, the provincial capital.

The majority of the deaths occurred in rural districts with poorly built houses south of Dingxi.

About 1,200 dwellings collapsed in the quake and some 21,000 others were damaged.

Up to 80 percent of the houses collapsed in towns, such as Meichuan and Puma, near the epicenter, officials said.

The powerful earthquake was followed by about 410 aftershocks, with the most powerful having a magnitude of 5.6 and occuring about 90 minutes after the temblor. EFE