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The death toll from the magnitude-6.6 earthquake that hit the northwestern Chinese province of Gansu on Monday has risen to 89, with five people missing and more than 600 others injured, officials said.

Seventy of the people injured in the powerful quake are listed in serious condition.

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

The majority of the province's cities were affected by the earthquake, with some towns still partially cut off from the outside world by power outages, officials said.

The quake's epicenter was at a depth of 20 kilometers (12.4 miles) 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, however, occurred in rural districts with poorly built houses south of Dingxi.

Minxian was the area most affected by the quake, with district officials reporting 87 dead and 515 others injured.

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

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

The earthquake was felt in Lanzhou and Xian, the capital of the neighboring province of Shaanxi.

The strong earthquake was followed by about 422 aftershocks, with the most powerful having a magnitude of 5.6 and occurring about 90 minutes after the temblor.

The powerful aftershock "caused many of the houses that survived the first temblor to collapse," an eyewitness told the official Xinhua news agency.

More than 2,000 soldiers, medical teams and about 300 police officers have been deployed in the disaster zone.

About 10,000 tents and 30,000 blankets were sent by officials for the approximately 27,000 people affected by the quake.

Rescue teams will do "whatever it takes" to find survivors, President Xi Jinping told the official CCTV network. EFE