Local authorities in Xinjiang, in China’s far west, said 21 people were killed in an armed standoff on Tuesday night in the deadliest incident in the restive region in more than a year.

The clashes in a rural town near Kashgar, China’s westernmost city, are an indication that the government is still struggling with resistance from the region’s indigenous Uighur ethnic group despite attempts at new policies.

The report in a statement from the regional government on its media portal said three social workers had discovered several “suspicious persons” and banned knives hidden in the apartment of a family they were visiting. When they called their superiors to report the incident, they were overpowered by the men. Community officials and police who subsequently arrived at the scene were also attacked in and around the apartment, the report said.