The quake struck at 6:34 a.m (Beijing Time), according to the China Earthquake Networks Center (CENC).
The quake struck at a depth of about 10 km, state-run Xinhua news agency reported.
It was followed by 5-magnitude earthquake at 8:31 a.m (Beijing time) around the same place in the Tibet Autonomous Region.
The second quake struck at a depth of about 6 km.
Reports of any casualties and damage are awaited.