Several people were injured on Saturday when violence flared on the Garvaghy Road in Portadown during a junior Orange parade. Protesting nationalists hurled petrol bombs and suspected blast bombs, stones and bottles at a police line separating the demonstrators from the parade and its loyalist supporters.
The police in riot gear, heavily backed up by the British army, responded by firing plastic baton rounds at the protesters.
According to the RUC, 11 police officers and at least three civilians were injured during the trouble.
The violence came just five weeks before the even more contentious Drumcree Orange march is due to parade the length of the nationalist Garvaghy Road.
The scale of Saturday's violence has raised further concern that the North is facing into another incendiary marching season.
There was further trouble yesterday when the homes of three Protestant pensioners living on the lower Garvaghy Road were attacked.
One was petrol-bombed, according to local people, and police moved in. There were no reports of injuries, although the area remained tense last night.
The RUC insisted that the weekend trouble was "clearly orchestrated". In a statement, the Assistant Chief Constable of the RUC, Mr Tom Craig, said: "Police officers came under sustained and vicious attack."
The Ulster Unionist Party leader, Mr David Trimble, blamed republicans for fomenting the trouble.
Mr Breandan Mac Cionnaith, of the nationalist Garvaghy Road Residents' Coalition, said the claims of orchestrated violence were "complete lies". "The reality is that the violence was initiated by the RUC when they baton-charged local people," he said.
Mr Gerry Kelly, a Sinn Fein north Belfast representative, accused the RUC of having attacked local nationalists. He said the Parades Commission decision to allow a junior Orange march pass near the nationalist end of the Garvaghy Road was "just incomprehensible, especially considering the present climate".
The first indication of impending violence came early on Saturday morning when the RUC and the British army moved into the predominantly Protestant lower Garvaghy Road.
It was immediately evident that the parade would not pass off without nationalist protest.
The early parade went ahead without incident, despite a demonstration by about 50 nationalists.
The young Orange members, bandsmen and supporters were able to travel on by bus to join a larger Orange demonstration in Bangor, Co Down.
But by early evening large numbers of nationalists and loyalists had gathered to prepare for the return parade. The violence, which began around 3.30 p.m., continued for several hours.
About 400 nationalists were involved in the protest.
As the rioting worsened through the evening a second line of police in riot gear and British soldiers was deployed nearby as back-up. This produced a further volley of missiles from some of the protesters.
The Orange parade was halted a few hundred yards from the trouble around teatime. A tense stand-off resulted between the RUC, bandsmen, loyalists and about 16 junior Orange members whose ages ranged between seven and 13. The parade was later allowed to proceed closer to the lower Garvaghy Road where it was again halted by police.
The stone-throwing, which was sporadic at that stage, increased in intensity when the parade came in view of the nationalists, according to eyewitnesses.
The RUC fired a number of plastic bullets, and the protesters responded by using iron grilles from nearby shops as shields in order to continue the attack on the police line.
Then the first of three dull explosions was heard. A female RUC officer suffered a leg injury when she was caught up in the explosion from one of these blast bombs.
As the violence continued the Orange parade was eventually allowed through to its dispersal point near the lower Garvaghy Road.
A number of loyalists tore down Tricolours from poles on Garvaghy Road during the trouble.
Nationalist rioting continued into the later evening, petering out around 9 p.m., as the RUC and British army began to withdraw from the area.
The Sinn Fein MP for Mid Ulster, Mr Martin McGuinness, accused the RUC of "provoking violence" by allowing the parade to "encroach" on the Garvaghy Road.
However, the Northern Ireland security minister, Mr Adam Ingram, responded by condemning the violence and saying that "the actions of those who protested were quite deliberately destructive and unacceptable".