Nine RUC officers were injured in another night of sectarian violence in Belfast last night.
A number of civilians were also hurt as rival nationalists and loyalists threw 28 petrol bombs in the Whitewell area.
One of the wounded policemen is being treated for a suspected broken jaw.
A senior RUC officer said the trouble was the worst the area has seen in years and he urged both sides to pull back before anyone is killed.
Three RUC mobile support units, along with British soldiers, were called to Whitewell in an effort to keep the nationalists and loyalists apart and to prevent another night of violent rioting.
Loyalists in the White City estate claimed nationalists started the violence, while local DUP councillor Ian Crozier said the Provisional IRA orchestrated the attacks.
He said the IRA arranged for busloads of nationalists to come to the area to attack Protestant homes.
However, Sinn Fein's Eoin O'Brien rejected Mr Crozier's claim and said loyalists are fuelling the tension.
"There's an orchestrated campaign by loyalists within some of these interface areas to kind of retrospectively justify their attacks on the nationalist community," he said.
Meanwhile, the RUC is investigating a pipe bomb attack in east Belfast last night.
British Army bomb disposal experts were called to the scene after the device exploded at the rear of a row of houses on Kyle Street. Nobody was injured in the blast.