The government's seismological bureau said the quake hit shortly after 8 a.m. in Lushan county in the city of Ya'an, home to China's famous pandas.
The news office for the Sichuan provincial government said on its official microblog account that two people were reported killed in Lushan and that two townships had suffered severe damages.
A state-run China News Service, quoting unnamed local media, said more than 100 people may have been killed or hurt in the earthquake.
The seismological bureau initially measured the quake at magnitude-7, while the U.S. Geological Survey recorded it at 6.6-magnitude, powerful enough to cause severe damage. Its depth was shallow, less than 13 kilometers or 8 miles, which could magnify the impact.
The official Xinhua News Agency said that the quake rattled buildings in the provincial capital of Chengdu 115 kilometers, or 70 miles, to the east.
There are reports that the airport in Chengdu was closed shortly after the earthquake, and
State-run China Central Television reported the Chengdu airport was temporarily closed, and that delays and flight cancellations were expected.
Social media users who said they were in Lushan county posted photos of collapsed buildings and reported that water and electricity had been cut off.
A man who answered the phone at the Ya'an city government said telecommunications were cut and that medical and rescue teams are on the way to the area.
"I felt the strong quake this morning in my office. All drawers of the desk opened and some stuff on the table fell on the floor," said the man, who refused to give his name, as is usual with low-ranking Chinese government officials.
The epicenter lies along the same Longmenshan fault where the devastating 7.9-magnitude quake struck in May 2008, leaving more than 90,000 people dead or missing and presumed dead.