Some 56 police officers were injured in overnight rioting in Belfast by Protestant Loyalist demonstrators, which the Northern Ireland police chief called "mindless anarchy." Four of the injured officers required hospital treatment, police said, according to dpa. The Loyalist protesters - who want Northern Ireland to remain British - were trying to disrupt a planned march by Republicans, who favour a united Ireland. Police said the officers came under "heavy and sustained" attack from protesters throwing bricks and bottles. Police used plastic bullets and water cannon, and made a number of arrests. Northern Ireland police chief Matt Baggott said the violence was "mindless anarchy" and "thuggery" and he paid tribute to what he said was the immense courage of his force. "The only people they [the rioters] are damaging is themselves," Baggott said. "It is their communities that are going to be condemned to another decade without hope, if not longer, this is only damaging their own community and that's the sort of message our politicians need to be getting out there." Some of the demonstrators accused the police of being heavy-handed. The unrest prevented the Republican marchers from using their planned route.