British Prime Minister Gordon Brown has described as "evil and cowardly" the attack on a Co Antrim army barracks in which two young soldiers were shot dead.
"No murder will be able to derail a peace process that has the support of the vast majority of the people of Northern Ireland and we will step our efforts to make the peace process one that lasts and endures," Mr Brown said.
Two gunmen shot dead two British soldiers and seriously injured four others, including two pizza delivery men, in a drive-by shooting at the Massereene Barracks shortly before 10pm last night.
The victims were taking delivery of a pizza when the attackers pulled up in a vehicle and opened fire.
Secretary of State for Northern Ireland Shaun Woodward condemned the shooting as an “act of criminal barbarism”.
He said: “The people who did this will be pursued and they can be assured that they will never be able stop political progress in Northern Ireland.”
British Home Secretary Jacqui Smith described the shooting as a “vicious and barbaric attack”.
She told Sky News: "Things like this won't be able to derail a process which has the support of the vast majority of people in Northern Ireland."
The attack happened just 36 hours after Northern Ireland Chief Constable Sir Hugh Orde confirmed that undercover soldiers had been called in to carry out surveillance operations on dissidents amid warnings that the threat against his officers and military personnel was at its highest for almost a decade.
Asked about Northern Ireland Chief Constable Sir Hugh Orde concerns, Ms Smith said: “We will make sure that wherever there are people who want to kill or maim in whatever name we will have the resources in place in order to prevent that from happening.”
She added: “In Northern Ireland real progress has been made through a political process that local politicians have been willing to work incredibly hard on and which the vast majority of people in Northern Ireland support.
“I think it is that which is going to be the real opposition to the sort of brutal killing of both civilians and armed forces that we have seen today.”
Shadow foreign secretary William Hague said the attack was evidence that some people in Northern Ireland wanted it to “go back into its old sectarian ways”.
He said: “It is astonishing there are people stupid enough, crazy enough to want that to happen.
“It means that everybody else, and that is the, I think, 99 per cent of the people of Northern Ireland, must make sure that doesn’t happen,” he added.
Liberal Democrat leader Nick Clegg said hearts went out to the family and friends of the soldiers “murdered so brutally” and wished the injured a speedy recovery.
Speaking to his party’s spring conference in Harrogate this afternoon, he said: “This attack is a reminder of Northern Ireland’s darkest days, which have no place in its present and future.”