Hong Kong riot police have used pepper spray to disperse protesters around government headquarters, fuelling tension ahead of a planned sit-in by protest against Beijing's tightening grip on the former British colony.

Clashes through the night between demonstrators and police carrying riot shields underscore the challenges China faces in shaping its vision for Hong Kong's future as a restive younger generation challenges its influence. Beijing last month rejected demands for people to freely choose the region's next leader in 2017.