Five officers of the Police Service of Northern Ireland were injured in the melee Friday evening in Newtownabbey, the Belfast Telegraph reported. None were reported to be seriously hurt.
Rioters attacked an Alliance Party office, breaking windows. The group, which aims to bridge the sectarian divide in Northern Ireland between the mostly Catholic Irish nationalists and mostly Protestant British loyalists, supported a successful effort by Sinn Fein in the Belfast City Council to limit the flying of the British flag at city hall to a few days a year.
A car was set on fire during the rioting.
Police said the trouble started when officers intervened to stop protesters from removing the tricolor flag of the Irish Republic from lampposts.
About three-quarters of the population of Newtownabbey, north of Belfast, are Protestant.