Four hundred extra police officers from Great Britain are being deployed to Northern Ireland after a night of serious loyalist rioting in Belfast that left more than 30 officers injured and an MP hospitalised.
More than 600 mutual aid officers from England, Scotland and Wales were already in the region supporting the Police Service of Northern Ireland (PSNI) operation as tensions surrounding the traditional Twelfth of July commemorations spiralled into disorder last night.
Trouble flared in the north of the city as police attempted to enforce a decision banning a controversial Orange Order parade from passing the republican Ardoyne area on the Crumlin Road. Disorder spread to east Belfast during six hours of violence.
The Orange Order had originally called for protests against the determination of the Parades Commission adjudication body but, in the wake of the violence, late last night senior Orangemen called for protest action to be suspended.
Democratic Unionist Party MP for North Belfast Nigel Dodds was taken to hospital after being struck in the head by a brick during the unrest on the Woodvale Road in his constituency.
PSNI Chief Constable Matt Baggott today condemned those responsible for the trouble.
"The scenes were both shameful and disgraceful," he said.
"We said that we were resolved to uphold the rule of law and the Parades Commission determination not to allow the return parade past the Ardoyne shop fronts. We did that. We did so impartially. We did so firmly.
"I cannot praise highly enough this morning the courage, the professionalism and the restraint of my PSNI colleagues, and those from England, Wales and Scotland who joined us in making sure the rule of law was upheld."
Mr Baggott also criticised those within the Orange Order who had called for protests.
He said they needed "to reflect on whether they provided the responsible leadership asked for by myself and by the (main political) party leaders.
"Some of their language was emotive and having called thousands of people to protest they had no plan and no control and, rather than being responsible, I think the word for that is reckless."
Mr Dodds, who was knocked unconscious when struck close to police lines, was discharged from the Royal Victoria Hospital in the early hours of this morning.
Petrol bombs, sticks, fireworks, drain pipes, and part of a wall were hurled at police. Some rioters even wielded swords.
In response officers fired baton rounds and deployed water cannon.
Chair of the Policing Board - the PSNI's oversight body - condemned the violence. Anne Connolly said: "There is no place in our society for violence against the police or any member of our community. The number of officers injured while doing their job is shocking and completely unacceptable."
She added: "It is important that those involved in disorder and violence understand that there are consequences to their actions and that they are charged and prosecuted. I would like to wish the officers and others who have been injured as a result of this violence a full recovery."
The Republic of Ireland's deputy premier and minister for foreign affairs Eamon Gilmore said: "The violence and disrespect for the rule of law we witnessed in Belfast last night is an affront to the decent people of that city and of this island.
"Our thoughts in particular are with those who were injured upholding the peace.
"The rule of law must be respected, even when people disagree with lawful decisions. The Police Service of Northern Ireland have our solidarity and unequivocal support in their efforts to protect people and property in Belfast."
He added: "Political and civil leadership must never equivocate on these matters. Clear leadership, shown now, can yet help avert further violence this weekend."