Loyalist rioters who attacked and injured police in a night of disorder at a sectarian interface in Belfast came prepared for violence, the officers' representative body 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 in a bid 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."
Riot squad officers from the Police Service of Northern Ireland (PSNI) bore the brunt of loyalist anger when they blocked access to the contested stretch of the Crumlin Road.
Within minutes of the parade reaching the police lines last night, empty bottles, bricks and metal bolts rained down on police.
At one point a number of loyalists broke through police barricades and started dancing on the bonnets of PSNI armoured Land Rovers.
Loyalist bandsmen played the sectarian Famine Song, which is played to the same tune as the Beach Boys' Sloop John B, but with anti-Catholic lyrics. They also played well-known loyalist tune The Sash.
Women and children mixed among the bandsmen and Orange Order members in the massed crowd barracking the police lines.
The violence followed a day of largely peaceful Twelfth of July holiday loyal order parades across the North - the highlight of the loyalist marching season.
There was a report of a bus carrying Orangemen being stoned in Greysteel, Co Derry, and police said a female officer was assaulted in Belfast city centre earlier in the afternoon.
The Twelfth demonstrations happened on Monday July 13 this year as the Orange Order does not stage its main event of the calendar on a Sunday.
A massive security operation had been mounted at the Woodvale/Ardoyne sectarian interface, where dissident republicans have gathered to attack police in the past.
The government-appointed Parades Commission - set up to rule on contentious marches - had issued a determination barring Orangemen from a section of the Crumlin Road.
Last year there was no rioting but, in 2013 - when restrictions were first imposed on the Orange parade - mass violence erupted in the unionist Woodvale area.
Since then, loyalists have manned a protest camp and staged nightly parades at Woodvale, requiring a policing operation costing millions.
In previous years republicans rioted when the parade was allowed to pass up the road on the way back from Belfast's main Twelfth commemoration.
Ahead of the Twelfth senior police commanders expressed concern that Orange Order and other loyalist groups had withdrawn marshals who helped keep the peace last year.
Unlike last year, there was not a joint call from a broad range of unionist and loyalist political parties, including two with links to paramilitary groups, for the Twelfth to pass off peacefully and lawfully.
However, there were calls for calm from individual political representatives and leaders of the Orange institution.
Sinn Féin's Gerry Kelly said people were "disappointed" the situation deteriorated into violence and appealed for community leadership.
PSNI chief constable George Hamilton said his thoughts were with the injured officers and teenage girl.
Shadow secretary of state for Northern Ireland Ivan Lewis said the violent scenes were a "serious step backwards for stability in Northern Ireland".
"Police and security professionals, as well as members of the public, have endured unacceptable levels of violence and disorder," he said.
"The small minority determined to return to the bad old days must not be allowed to prosper. Politicians and community leaders should reiterate their support for the rule of law and condemn the violence without fear or favour."