Loyalist rioters who attacked and injured police in a night of disorder at a sectarian interface in Belfast came prepared for violence, the officers' union has said.
The Police Federation said disturbances that left eight officers injured, including one who needed 12 stitches for a bite wound, were "mindless, deplorable and shameful".
Officers were pelted with bricks, bottles, metal ladders, bolts and masonry when a parade returning from traditional Twelfth of July Orange commemorations was prevented from marching from the unionist Woodvale area toward the adjacent nationalist Ardoyne.
As loyalists attacked police on the unionist side of the police line, on the nationalist side a 16-year-old girl standing in a crowd was injured when she was apparently struck by a car.
Chaotic scenes ensued as police lifted the vehicle off the girl. The driver has been arrested and police have said the girl's injuries are not life threatening.
Police deployed water canon to try to quell the loyalist unrest at the notorious sectarian flashpoint in the north of the city.
Police Federation NI chairman Mark Lindsay said: "These rioters had obviously come prepared to cause disorder.
"Once again, officers demonstrated their patience and professionalism even though their lines were under attack.
"The scenes we witnessed were deplorable and shameful. The behaviour of those who viciously targeted police lines was mindless and unacceptable.
"Like others, I would appeal for calm. My thoughts are with my colleagues who were injured and those hundreds of officers who continue to work to bring order to challenging interface areas."
The Orange Order also condemned the rioters.
"Those involved in violence should desist," said a spokesman for the Grand Orange Lodge of Ireland.
"It is not only counter-productive but also plain wrong. Such actions are only strengthening the hand of those who wish to further curtail our parades."
Northern Ireland Secretary of State Theresa Villiers said: "I condemn these disgraceful attacks on the police. Those responsible do nothing to further the cause they claim to promote. They damage Northern Ireland and wreck a day which should be about respectful celebration of cultural tradition.
"My thoughts are with all those injured."
The violence followed a day of largely peaceful Twelfth of July holiday loyal order parades across Northern Ireland - the highlight of the loyalist marching season.
Sinn Fein's Gerry Kelly said people were "disappointed" the situation deteriorated into violence and appealed for community leadership.