Thousands of emergency workers, including soldiers, rushed to reach the affected zones in the hilly region, and Chinese Premier Li Keqiang traveled to the area from Beijing, state media reported.

Xu Mengjia, the Communist Party chief of Ya'an, the city that administers the area where the quake struck, told state broadcaster CCTV that because of landslides and disruption to communications, determining the total number of casualties may take some time.

Students gather outside to escape the quake 

The quake struck just after 8 a.m. local time Saturday, about 115 kilometers (70 miles) away from the provincial capital, Chengdu, at a depth of around 12 kilometers, according to the U.S. Geological Survey. There was conflicting information about the earthquake's strength, with the USGS putting the magnitude at 6.6 and the China Earthquake Networks Center gauging it at 7.0.

It was followed by a series of aftershocks, some of them as strong as magnitude 5.1, the USGS said.

Authorities have responded by sending rescue workers to the area around the epicenter, briefly halting flights at the airport in Chengdu and suspending high-speed rail operations, state media reported.

The event stirred memories of the devastating earthquake that hit Sichuan in 2008, killing more than 87,000 people.

First responders to Saturday's quake reported that the damage caused didn't appear to be as severe as what was seen in the aftermath of the 2008 disaster, according to CCTV.

Fan Xiaodong, a student in Chengdu, said when the tremors began to shake buildings in the city, many of his startled classmates rushed out of their dorms, some of them wearing only the clothes they'd been sleeping in.

At first, Fan said, he only felt a slight trembling as he dozed in bed.

"I thought it was my roommates shaking the bed," he said. "But the shock became stronger soon, and it came to me that an earthquake happened."

The epicenter was in Lushan country, a district of Ya'an. That area is home to China's famous giant pandas and houses the country's biggest panda research center.

CCTV reported that the pandas at the facility, which is about 40 kilometers (about 25 miles) from the epicenter, were safe.

Residents of Chongqing, a sprawling metropolis more than 300 kilometers (about 190 miles) from Ya'an, said the quake also shook buildings there.