Officials said no casualties have been reported so far.
The quake, with a focal depth of just five kilometres, was felt strongly in Jinggu Dai and Yi Autonomous County in Yunnan province, which has a population of 290,000, state-run Xinhua news agency reported.
The quake shook buildings for several seconds. Residents have been evacuated to open areas, a local official said.
Some phone calls to Jinggu went unconnected.
Pictures posted on the internet show cracks on walls.
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The China Earthquake Networks Centre said the epicentre was monitored about 67 kms away from Lincang city and 85 kms away from Pu'er city.
A 6.5-magnitude quake in Ludian, Yunnan, on August 3 had killed more than 600 people.
Back in 1970, a strong 7.7-magnitude quake in Yunnan had killed at least 15,000 people.
