It was 67 kilometers (41 miles) west of Murghob, Tajikistan, and 20 kilometers (12 miles) below ground, according to the U.S. Geological Survey.
Mughrob is the district capital with a population of a few thousand people high in the Pamir Mountains.
The strong quake originated at a depth of 10 kilometers (6 miles), reported Chinese state television CCTV, citing the China Earthquake Networks Center.
The epicenter is about 82 kilometers from the nearest border with China and was strongly felt in some areas in China's western Xinjiang region, including Kashgar and Artux, CCTV reported.
However, no casualties or damage has been reported so far, state media added, citing local information officers.
Power supply and communication remained normal in Kashgar, state media Xinhua reported.
The Xinjiang railroad department called a halt to passenger trains running on the Aksu to Kashgar section of the Southern Xinjiang railway, state media said.
Local authorities were inspecting bridges, tunnels and signal equipment, CCTV said.
Experts have long warned of the risks of a major earthquake in Tajikistan.
They voiced worry, particularly over Lake Sarez, which formed as a result of a major earthquake in 1911, saying it could pose a major threat in the future.
The lake is located behind a natural dam deep in the Pamir mountains, and if the dam is breached, the consequences will be catastrophic.
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