There were disturbances at three locations in Belfast as a contentious Orange Order parade began this afternoon in the west of the city.
Police were deployed in the Short Strand and Grosvenor Road area where the Whiterock parade is due to pass. Protesters and supporters of the march clashed amid anger over the re-routing of the parade.
A mob attack on a Catholic man overnight in the Short Strand, linked by local representatives to sectarianism arising out of the parade, is likely to have created further tensions. The man is in a critical condition in hospital.
There were also disturbance on the Albertbridge Road as thousands lined the loyalist Shankill Road to see the parade pass.
Loyalist threw blast bombs and petrol bombs at police leaving at least two officers injured. As ambulances were called in, a police water canon was used to douse mobs who launched a sustained assault along the West Circular Road.
Earlier loyalists threatened traffic chaos as roads were blocked off across the city. They also clashed briefly with nationalists protesting against the march.
The trouble was rapidly contained by police in riot gear drafted in as part of a massive security operation.
Security chiefs were expecting trouble and established a major presence along the route of the parade. Orangemen and their supporters have been angered by a Parades Commission decision to reroute parade from part of the Springfield Road following nationalist residents' objections.
As both sides psyched themselves up for a tense day, Assistant Chief Constable Duncan McCausland appealed to community leaders to use their influence to ensure the march passes off peacefully.
"No one wants to see a situation where a parade or protest descends into violence and disorder," he insisted.
"It is the responsibility of each and every one of us to do our best to avoid that. I am concerned that today could bring some disorder but I am also hopeful that common sense will prevail."
Loyalists have mounted a series of street protests all week in north and west Belfast during the morning and evening rush hour following the Parades Commission's ban on today's parade passing through security gates on the Springfield Road.
Orangemen are being asked instead to march through the site of the former engineering firm, Mackies. A feeder parade on a non-contentious part of the Springfield Road will be allowed.
Before thearch, Gerry Adams appealed for calm in the face of "those who are intent on whipping up sectarian tensions around this parade".
Democratic Unionist leader, the Rev Ian Paisley, Ulster Unionist leader Sir Reg Empey and the Orange Order have in recent days lobbied the Government in a bid to have the ruling overturned and have lambasted the commission's decision.
Orange County Grand Master Dawson Bailie claimed yesterday despite postponing a march through the area in June and undertaking other initiatives, the Order was being denied basic rights.
"In spite of all the risks taken, the responsible leadership shown and the pain suffered by the local communities, the parades forum and the Orange Order are faced with yet a further attempt to humiliate and suppress our culture," he said.
Sean Paul O'Hare of the nationalist Springfield Residents Group appealed for calm on all sides.
A large police presence is expected later tonight when a major protest rally is due to take place.