The Real IRA -- a dissident group of the Irish Republican Army -- has claimed responsibility for the ambush on British soldiers at Massereene army barracks near Belfast, which left two men dead and four injured.
Northern Ireland is in shock over the return of violence
A caller to the Dublin-based Sunday Tribune claimed responsibility for the shooting in the name of the South Antrim brigade of the Real IRA.
"He said he made, and the Real IRA made, no apology for targeting British soldiers while they remained what he called occupying the north of Ireland," Suzanne Breen, a journalist at the newspaper, told Sky News on Sunday, March 8.
The two soldiers were shot dead late on Saturday, as the army base north of Belfast took delivery of takeaway pizzas. Four other people, including two pizza delivery men, were seriously injured. One is said to be in critical condition.
The caller also claimed that the pizza delivery men were "collaborating with British rule" by serving British soldiers, Breen was quoted by the Irish Times as saying.
British authorities started a massive manhunt
The governments in Northern Ireland, London and Dublin have sharply condemned the shooting.
"The whole country is shocked and outraged at the evil and cowardly attacks," said British Prime Minister Gordon Brown. "I can assure you that we will bring these people to justice."
"No murderer 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 up our efforts to make the peace process one that lasts and endures," added Brown.
Northern Ireland's First Minister Peter Robinson has postponed a planned trip to the United States to respond to the tragedy.
Irish Prime Minister Brian Cowen said that "a tiny group of evil people cannot and will not undermine the will of the people … to live in peace together."
Attempt at mass murder
The British army officially ended its mission in Northern Ireland in 2007 after 38 years
Gunmen reportedly entered the base as pizzas were delivered and fired up to 40 shots in two long bursts of gunfire.
"I have no doubt in my mind that this was an attempt at mass murder," said Derek Williamson, the investigating police officer.
Northern Ireland's police chief, Sir Hugh Orde, had warned earlier this week that the threat from dissident republicans was at its highest in nearly a decade, amid reports that British special forces were back in the region to gather intelligence.
Saturday's shooting is the first deadly attack on the British military in Northern Ireland since the signing of the Good Friday peace deal in 1998.
Shadow cast on compromise government
Republican dissidents are suspected, though no one has claimed the attack
Concerns have been raised over the stability of the current power-sharing government, which unites former arch enemies across the Protestant-Catholic divide.
"This has taken us back into bad, bad old days that we have long since left behind us," Thomas Burns, a lawmaker with the nationalist SDLP told BBC television.
More than 3,000 people were killed in the conflict between nationalist Catholics and loyalist Protestants in Northern Ireland, which began in the 1960s and continued for three decades. The last British military death in the conflict was in 1997 and the Good Friday Agreement was signed the following year.
In 2007, the mainly Protestant Democratic Unionists, which want Northern Ireland to remain part of Britain, and the Catholic Sinn Fein, which supports integration into the Republic of Ireland, established the present power-sharing government, which has devolved power from London.