Ministers from the Northern Ireland Executive and the Irish Republic's government discussed the murder of prison officer David Black today at a North South Ministerial Council meeting in Armagh.
Speaking after the meeting, Irish prime minister Taoiseach Enda Kenny said:
Northern Ireland's deputy First Minister Martin McGuinness has said supporters of dissident republicans need to "get real" and realise they are a "ragbag" of criminals out for their own ends.
Speaking after the murder of prison officer David Black yesterday, Mr McGuiness said they swim "in a sea of criminality and drugs" while wrapping themselves in a flag of political convenience.
"People need to get real. They need to recognise the danger that a tiny number of people can represent to human beings and they need to recognise that the world has changed, that over the course of the last 15 years we have built something, all of us together, which we can be very proud of."
Earlier, the Sinn Fein veteran and First Minister Peter Robinson stood shoulder to shoulder with Irish prime minister Taoiseach Enda Kenny and his deputy Tßnaiste Eamon Gilmore after a meeting in Armagh as they jointly denounced the killing.
Asked about the motive behind the attack of prison officer David Black, Northern Ireland Secretary Theresa Villiers told the House of Commons:
Sue McAllister, director-general of the Prison Service in Northern Ireland, met David Black's grieving widow, Yvonne, at her home in Cookstown, Co Tyrone, today.
Mrs Black was meanwhile praised in the House of Commons for her response to her husband's brutal murder.
The Democratic Unionist Party's Westminster leader Nigel Dodds paid tribute to her "brave and courageous words" in calling for no retaliation.
Northern Ireland Secretary Theresa Villiers said Mrs Black's stance was "courageous and entirely right".
The US ambassador to Britain, Louis Susman, has been briefed on the killing of prison officer David Black in Northern Ireland, Theresa Villiers has said.
The Northern Ireland Secretary said Mr Susman added his condemnation of the atrocity.
Mrs Villiers also said US secretary of state Hillary Clinton, whose husband Bill played a key role in the 1998 Good Friday Agreement peace deal when he was president, "retains a close and strong interest in Northern Ireland".
She added: "I'm sure she shares the concern that has been expressed in the House today."
Northern Ireland Secretary Theresa Villiers, though, said the "horrific" murder of prison officer David Black would not succeed in returning the country to the "dark days of the past".
In an urgent statement to MPs, Northern Ireland Secretary Theresa Villiers sent her "deepest condolences" to David Black's widow Yvonne, son Kyle and daughter Kyra for their "devastating loss" and vowed to catch his killers.
"The Government will do whatever we can to help the PSNI bring the perpetrators of this atrocity to justice," she said. "We will continue to do everything in our power to ensure the terrorists do not succeed."
Mrs Villiers said yesterday's killing showed the threat posed by dissident republicans.
"The numbers involved in terrorism activities are small, but these groupings have the capability and they have lethal intent," she said. "They can still ruin lives despite their lack of support in the community, so we remain vigilant."
The Government will do "whatever we can" to help bring prison officer David Black's killers to justice, Northern Ireland Secretary Theresa Villiers has told the House of Commons.
Northern Ireland Secretary Theresa Villiers will make a statement in the House of Commons at 11:00am following yesterday's murder of prison officer David Black.