LONDON — Northern Ireland's main Catholic and Protestant parties on Wednesday condemned street violence that saw shots fired in what police called a "blatant bid to murder police officers."

Police said that six shots were fired at officers during a fourth night of disturbances in Northern Ireland's second-largest city, also known as Derry. No officers were injured.

Chief Inspector Neil Beck said "around 16 petrol bombs and five paint bombs were thrown ... and, in what can only be described as a blatant bid to murder police officers, shots were fired at police close to our city's walls."

Summertime violence used to be common in Northern Ireland, especially around parades culminating each July 12 by the Orange Order, a Protestant brotherhood that is despised by much of Northern Ireland's Irish Catholic minority. But conflicts have fallen sharply in recent years.

Authorities accused dissident Irish republican groups opposed to Northern Ireland's peace process of fueling the latest violence.

In a rare joint statement, the pro-British Democratic Unionist Party, Irish nationalist party Sinn Fein and the smaller Ulster Unionists, SDLP and Alliance parties said "there must be a strong, clear and united voice against those who would engage in such disgraceful violence."

"As a society we must all stand with those who maintain law and order and who protect all sides of our community," the statement said.

Mark Lindsay, chairman of the Police Federation for Northern Ireland, said "attacks like this have got to stop. We have to see an all-out effort being made to rid communities of these 'dinosaurs' and to allow people to get on with their lives."