Rescue and relief efforts are under way and a working group has been dispatched to assess the impact of the disaster, state media said, with the number of missing people in the quake's aftermath unknown.
Earthquakes are common in western provinces such as Gansu, which lie on the eastern boundary of the Qinghai-Tibetan plateau, a tectonically active area. China's deadliest quake in recent decades was in 2008 when a magnitude-8.0 temblor struck Sichuan, killing nearly 70,000 people.
The epicentre of the latest quake was 3.1 miles from the border between Gansu and a neighbouring province. Strong tremors were felt in many parts of Qinghai province, the official Xinhua news agency said.
China's national commission for disaster prevention, reduction and relief and Ministry of Emergency Management have activated a level-IV disaster relief emergency, Xinhua reported.
As the disaster area is in a high-altitude region where the weather is cold, rescue efforts are working to prevent secondary disasters caused by factors beyond the quake, Xinhua said.
