URUMQI, China—This city on China’s Central Asia frontier may be one of the most closely surveilled places on earth.

Security checkpoints with identification scanners guard the train station and roads in and out of town. Facial scanners track comings and goings at hotels, shopping malls and banks. Police use hand-held devices to search smartphones for encrypted chat apps, politically charged videos and other suspect content. To fill up with gas, drivers must first swipe their ID cards and stare into a camera.

China’s efforts to snuff out a violent separatist movement by some members of the predominantly Muslim Uighur ethnic group have turned the autonomous region of Xinjiang, of which Urumqi is the capital, into a laboratory for high-tech social controls that civil-liberties activists say the government wants to roll out across the country.

It is nearly impossible to move about the region without feeling the unrelenting gaze of the government. Citizens and visitors alike must run a daily gantlet of police checkpoints, surveillance cameras and machines scanning their ID cards, faces, eyeballs and sometimes entire bodies.

When fruit vendor Parhat Imin swiped his card at a telecommunications office this summer to pay an overdue phone bill, his photo popped up with an “X.” Since then, he says, every scan of his ID card sets off an alarm. He isn’t sure what it signifies, but figures he is on some kind of government watch list because he is a Uighur and has had intermittent run-ins with the police.