The aftershock hit the county of Mianzhu at 5:26 p.m. local time (9:30 GMT), the agency said, citing the China Earthquake Administration. No details on casualties or damage have yet been released.
Chinese authorities say that the latest earthquake is not likely to cause new deaths, as most people in the area have been evacuated.
The quake comes two months after the province was hit by the worst earthquake to hit China in three decades, measuring 8.0 on the Richter scale. At least 70,000 people were killed and 10 million displaced.
The May 12 quake, which affected more than 47,000 villages, has left some 1.4 million people in remote villages completely impoverished. China's direct economic losses from the earthquake have exceeded one trillion yuan (around $150 billion).