Calm has returned to Kashgar in the Xinjiang Uygur autonomous region following a deadly terror attack that left 21 dead.

The clash, described by the region's information office as a "severe, violent, terror incident", happened after three community workers in Selibuya township, Bachu county, found several suspicious people and knives in a house on Tuesday.

They reported the details to their supervisor but were then restrained by suspected terrorists, according to the Xinjiang government's information office.