Many city centre workers went home early on hearing of roadblocks, as loyalists sent bogus messages, purporting to come from the police, to businesses and shops.
The new tactic followed two days and nights of disruption in the city and surrounding towns, as Protestant hardliners continued to protest against the re-routing of an Orange Order march away from a nationalist part of west Belfast on Saturday.
More than 50 police officers were injured in the first two days as members of paramilitary groups such as the Ulster Volunteer Force (UVF) and Ulster Defence Association (UDA) attacked with guns, blast bombs and fire bombs.
Early yesterday several areas of the city resembled war zones, their streets strewn with bricks, torched cars and the remains of burning barricades. A bank on the northern outskirts of Belfast was among a number of premises destroyed in the rioting.
Damage to buses alone is estimated to be in the region of £500,000. In east Belfast, rioters commandeered a digger from a building site and drove along a major thoroughfare, knocking down lamp-posts and bus stops and demolishing a wall.
Ten people appeared in court in Belfast and Ballymena yesterday on charges of riotous assembly and riotous behaviour. Eight were remanded in custody.
The Northern Ireland Secretary, Peter Hain, is expected to "specify" the UVF, thus formally declaring that its ceasefire is regarded as being at an end.
Local authorities are reluctant to take such steps, regarding it as important and potentially valuable to keep open lines of communication to the illegal groups.
But the UVF has not only killed four people in feuding in recent months, but has also been behind much of the rioting, which has been among the worst seen in Belfast for some years. Its ceasefire is now regarded as close to meaningless.
Mr Hain said he was horrified by CCTV footage, provided to him by police, showing loyalists attacking police and troops. He said: "The evidence I have seen this morning is absolutely clear-cut. If it wasn't clear-cut before, it's absolutely categorical now. As a result, I'm now going through, and indeed have been over the past week, a process in which I will be making an announcement in the next few days."
As the disruption goes on, unionist politicians have come under criticism for their reaction to the violence. The senior US State Department figure Mitchell Reiss said unionist leaders had "abdicated responsibility," accusing them of failing to provide leadership.
The Orange Order's Belfast grand master, Dawson Bailie, refused to condemn the violence. He said: "As far as I'm concerned the people to blame for that are the Secretary of State, the Chief Constable and the Parades Commission, firmly and squarely. I'm not condemning anything at all at this moment in time."
The Sinn Fein president, Gerry Adams, accused the Reverend Ian Paisley of the Democratic Unionist party and the Ulster Unionist leader, Sir Reg Empey, of giving "wrong and negative leadership". He said they could not wash their hands of what had happened.
Mr Paisley defended his predictions that the rerouting of the parade "could be the spark which kindles a fire there would be no putting out". He said he had been very worried about the situation, adding: "At that time I was in the midst of trying to get a way whereby this would not happen. And it has happened - my words have been proved to be right."Reuse content