The US Geological Survey said the quake hit at a depth of about 6 miles about 36 miles northeast of Nyingchi.
China's official Xinhua News Agency put the magnitude at 6.9 and said it struck at 6.34am local time.
The Nyingchi government said in a statement on its microblog that the quake's epicentre was in an uninhabited region and that it had yet to receive any casualty reports.
The epicentre was within 150 miles of the Indian towns of Along, Pasighat and Tezu, the USGS added.
A magnitude 6.3 quake is considered strong and is capable of causing severe damage.
Southwestern parts of China are frequently hit by earthquakes. A huge quake in Sichuan province in 2008 killed almost 70,000 people.
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