Chinese state media said shaking was felt in major cities in the region, including in the Sichuan provincial capital Chengdu and the metropolis of Chongqing.
The China Earthquake Administration said there were several aftershocks.
Pictures posted by state media on their social media accounts showed cracks in some buildings and people rushing into the streets in some cities in Sichuan.
State television said rescuers had reached the epicentre - a largely rural area - and had pulled some people out of rubble alive already. At least one person so far has died, the report added, without giving details.
A huge quake in Sichuan in May 2008 killed almost 70,000 people.
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