NATIONALIST reaction ranged from charges of British government bad faith and RUC brutality from Sinn Fein to calls for people to stay calm and off the streets from the SDLP leader, Mr John Hume.
The Sinn Fein MP, Mr Martin McGuinness, said: "The Blair government has failed its first test miserably."
The nationalist community was "seething with anger at the imposition of virtual martial law and the brutal fashion in which it was enforced by the RUC and British army against the innocent people of the Garvaghy Road.
"Mo Mowlam has learned her predecessors' lesson of bad-faith negotiations well and quickly. She promised publicly that she would deliver her decision personally to the Garvaghy residents. This she failed to do," he added.
"Once more a British government has shown the world that nationalists in this state are treated as and considered second-class citizens. Ronnie Flanagan's admission that he made his decision based on information that loyalist paramilitaries would kill Catholics is a stark admission of surrender and shows that the RUC cannot function impartially. He should resign and the RUC should be disbanded."
Mr Hume said it was evident to Northern nationalists and the world that the British government had not made the right decision. The situation in Portadown was "a deep symptom of our problem, and our problem is the suspicion and distrust of one section of the community by another and the failure to reach agreement that would respect our differences".
Reaching accommodation would require "new thinking, not the old thinking which is a victory for one side or the other". He called the Garvaghy Road march a "terrible symptom of the deep disease of Northern Ireland - a divided society.
"Let us concentrate our minds and hope that the anger that was caused by today will not lead to violence. I appeal to people not to let that anger express itself in any destructive way and for people to remain calm and to stay off the streets."
The Workers' Party president, Mr Tom French, also called on people to "be calm and show restraint", adding "now is the time for those genuinely seeking solutions to problems such as contentious parades and their outcome to continue with dialogue and try to halt mindless violence".
The Green MEP, Ms Patricia McKenna, who with Mr Trevor Sargent TD was in Portadown as an observer, condemned the use of excessive force by the RUC and the British army. "The security forces behaved in a way that was deliberately provocative," she said. "I witnessed plastic bullets being fired at eye level and people being beaten with batons. Such use of plastic bullets was a flagrant breach of the RUC's own guidelines."
A New Hampshire state representative Mr Robert Cushing, another observer invited by the local nationalist community, said he had been shocked to see a community "occupied by military force" with people "beaten off the streets, put into their houses, batoned all the way down to the end of the road".
The Lower Ormeau Concerned Community condemned the "savage and brutal behaviour" of the security forces, and said yesterday's events "have only strengthened our resolve and determination that there will be no Orange Order march along the Lower Ormeau".
The Irish Republican Socialist Party called on nationalists to break off contacts with the British government in the North.
A Belfast SDLP councillor, Dr Alasdair McDonnell, was challenged on radio to condemn the violence of the residents against the security forces and did so, saying it "only takes away from the grievous injury suffered by some of those people on the Garvaghy Road during the night".