Taoiseach Brian Cowen has again condemned 'in the strongest terms' the attack at a military base in Co Antrim that left two British soldiers dead.
The Taoiseach, speaking outside Government buildings this evening, described the killings as murder and said it was an attack on the peace process and the democratic institutions.
"These people have no support. They will not succeed. Their actions are entirely futile," he said.
Mr Cowen emphasised that the response by both governments, the two police forces, the Northern Ireland executive and all parties north and south of the border would be "seamless".
"We all remain united and steadfast, both governments, all the parties and most importantly, the entire community in Northern Ireland are resolved to win our hard-won peace on this island," he said.
The Taoiseach was speaking to reporters outside Government Buildings this afternoon. He said he had spoken today with British prime minister Gordon Brown; first minister Peter Robinson; and deputy first minister Martin McGuinness about the attack.
He said Minister for Justice Dermot Ahern and Minister for Foreign Affairs Micheál Martin would meet with the Northern Secretary Shaun Woodward in the next few days. He said that Garda Commissioner Fachtna Murphy would also meet with PSNI chief constable Huge Orde, and that both police forces were jointly operating seamlessly.
"We will all do everything possible to ensure that those responsible for this awful atrocity are brought to justice as swiftly as possible," he said.
Asked about the information Garda intelligence had gathered in relation to dissident republic activity, Mr Cowen said: "Despite the success of the peace process there has been no reduction in the monitoring by gardaí of dissident republican activity. Indeed extensive and intensive resources are used to deal with that threat on an ongoing basis.
"It's a matter of public record that there have been many successes in that monitoring and surveillance of potential actions by dissident republicans. They have been able to halt their activities on a number of occasions. That will continue," he said.
Asked his opinion on comment that the decision to deploy British Army intelligence specialists in the North may have prompted the attack, Mr Cowen said: "I think operational responsibility for policing matters rests with the chief constable and with the Garda Commissioner in terms of our own jurisdiction. We would be supportive of any necessary efforts that are made to ensure that the surveillance is carried out and that the prevention of crime for dissident activity is successful."
When asked if he had any issue with the use of army intelligence, he said: "What we want to see is the appropriate expertise being deployed in the appropriate way. I think that's what the chief constable has in mind."
Mr Cowen was also asked about Sinn Fein¿s response to the killing, which some critics asserted was low-key and conditional. Mr Cowen did not accept that assessment.
"I have spoken with [Martin McGuinness] and have heard what has been stated in public [by Sinn Fein]. There is absolutely no equivocation in my view only that everybody regards this as totally futile and wrong and something that should not happen, an attack on the peace process itself. And I think it's important to make that point," he said.
Speaking in Cork, Minister for Foreign Affairs, Micheál Martin said he was confident the political institutions in Northern Ireland were well enough developed to survive any attempt to undermine them.
Mr Martin said Saturday's shootings were “a very callous murderous attack on soldiers and civilians” and said that there was “absolutely no basis for this type of behaviour”.
Earlier, British prime minister Gordon Brown said the political process in the North remained "unshakeable" despite the brutal killings of the two young British soldiers.
Mr Brown today met First Minister Peter Robinson and Deputy First Minister Martin McGuinness in the wake of the Real IRA attack in Co Antrim on Saturday night which left two dead and four others injured.
He said the killing of the two soldiers would not halt the peace process.
"What I've seen this morning is the unity of the people of Northern Ireland and the unity of the political parties, that they stand united behind the peace and political process that they've been building for many, many years," he said.
"They want to send out the message to the world, as I do, that the political process will not and can never be shaken," he added. "The political process is now unshakable."
Mr Brown visited Massereene Barracks in Co Antrim where the two soldiers were killed in the gun attack. He was accompanied by the North's Chief Constable Sir Hugh Orde on his visit to Massareene.
Mr Brown met Sir Hugh and political leaders at Stormont and was expected to urge Mr Robinson and Mr McGuinness to stand united in the face of the dissident threat.
Tributes were paid today to the two soldiers who were named as Sapper Mark Quinsey (23) from Birmingham, and Sapper Patrick Azimkar (21) from Wood Green, north London, both of 38 Engineer Regiment.
Northern Ireland¿s most senior British soldier paid tribute today to the two "magnificent" servicemen. Brigadier George Norton condemned the ¿callous and clinical attack".
Mr Robinson told the Stormont Assembly the murders represented a "challenge" from those who sought to destroy society.
"This is a moment of truth for us all. We all have a choice to make. On Saturday night the challenge was issued. Today, in this House and outside of it, let the answer be loud and clear "we are not turning back", he said.
Ulster Unionist leader Sir Reg Empey said he regretted the initial "ambiguity" from the Sinn Féin leadership. He said this was an opportunity to prove that "we have moved on and are putting the past behind us".
Earlier Sinn Féin president Gerry Adams urged members of the republican community to help police in their efforts to catch the killers.
"The logic of our position that is that we support the police in the apprehension of those involved," he said
However, Mr Adams strongly condemned the decision by Northern Ireland Chief Constable Sir Hugh Orde to bring in undercover soldiers from the Special Reconnaissance Regiment to monitor the activities of dissident republicans.
The US condemned the attacks in a statement last night. State Department spokesman Robert A. Wood sent condolences to the families of the murdered soldiers.
"The United States condemns the attack in Co Antrim, Northern Ireland, on Saturday night that resulted in two deaths and injuries to others.We call on all parties in Northern Ireland to unequivocally reject such senseless acts of violence, whose intention is to destroy the peace that so many in Northern Ireland have worked so hard to achieve," he said.
Two other servicemen and two pizza deliverymen - one named as 19-year-old local Anthony Watson and the other a 32-year-old Polish national - were also seriously injured in the shooting, which sent shockwaves through the peace process.
Meanwhile, the Polish pizza delivery man who was shot a number of times during the attack is no longer critically ill, according to a PSNI spokeswoman. His condition is now described as serious but stable. Two other soldiers and a second pizza delivery man remain in a serious condition in hospital.
British army technical officers were today continuing to examine a Vauxhall Cavalier believed to have been abandoned by the gunmen amid fears it could be booby-trapped.
The vehicle was dumped in the Ranaghan Lane area of nearby Randalstown late on Saturday night.
The two soldiers and two of their colleagues were shot when they went to the gates of the Massereene base to receive separate pizza deliveries around 9.20pm on Saturday.
Two masked gunmen opened up with bursts of semi-automatic rifle fire. At least one gunmen fired a second burst while the fatally injured soldiers lay on the ground.
Additional reporting: PA
