The Northern Secretary has said the reputation of the North has been "dragged through the mud" by events in Ardoyne.
Dr John Reid, who cut short his holiday and is due to return to the North today, said the protests had to stop immediately and dialogue had to begin.
Referring to the loyalist pipebomb attack on pupils of the Holy Cross School, Dr Reid said "any legitimate grievances of protesters have been drowned out by this violent sectarian bigotry".
"Children should not have to pay the price of the failure of adults to live together in peace," he said. "Neither should the police who have sustained serious injuries in recent days."
"What we have seen develop in the past few days is the path to barbarism. I cannot believe the people of north Belfast want that. I believe most of them want their elected representatives and community leaders to talk together and talk now," he said.
The Sinn Fein MLA for North Belfast, Mr Gerry Kelly, said it was important to focus on those behind the pipe-bomb attack. "Now we have children not only being threatened by the UDA but they have been attacked with a blast bomb.
"This is an organisation sitting down, thinking this thing out and deciding between yesterday and today to throw a blast bomb at these kids. This is anti-Catholic pure bigotry," he said.
Mr Alban Maginness, the SDLP Assemblyman for the area, said the attack was a "callous act" which could have injured the children. He said the blockade was unsustainable.
"I don't think it will last much longer," he said. "There's a deep well of anti-Catholicism here akin to anti-Semitism across the world and that's what's behind this."
Ms Eileen Bell, the Alliance Party deputy leader, said: "It is as clear as day that the children do not deserve the threatening abuse and violence they are facing daily," she said.
Mr Frazer Agnew, an independent unionist MLA for North Belfast, said the violence "merely takes away from the fascist nature of the insidious plan to ethnically cleanse the upper Ardoyne area of Protestants".
The north Belfast Women's Coalition representative, Ms Elizabeth Byrne-McCullough, called for "a search for constructive solutions in the Ardoyne standoff".