Western Cape police are monitoring the township of Nduli in Ceres, after a series of service delivery protests which erupted on Sunday.
It is understood that the unrest related to the provision of electricity and housing.
During the protests, an unknown group of people set alight a post office in Chris Hani Avenue and the old Nduli police station (now municipal offices), said Captain FC van Wyk on Tuesday evening.
He said protesters blocked roads with stones and tyres, as well as threw stones at police officers.
Van Wyk said two officers sustained minor injuries on Monday, amid action to disperse "the riotous crowd".
Seven people were arrested on charges of public violence.