Read more: Mother begs that son's murder is not in vain

Read more: Northern Irish policeman murdered in dissident bomb attack in Omagh

Former Provisional activists have been blamed for the murder of Ronan Kerr, a newly qualified Catholic police officer, in Omagh on Saturday.

Sources on both sides of the Irish border have pointed the finger of blame at a local faction of Real IRA anxious to make their mark ahead of Stormont elections and the Queen’s visit to the Republic.

The Police Service of Northern Ireland are already investigating the movements of known Republican dissidents in the Omagh area.

PSNI chief Matt Baggott has promised that no stone will be left unturned after Saturday’s car bomb killed GAA member Kerr as he prepared to leave for his first day in a new job at Enniskillen Police Station.

Baggott, who has described the 25-year-old Kerr as a ‘modern day hero’, has already ordered detectives to track down the dissidents responsible for his killing.

“This murder of our colleague was carried out by a potent and dangerous minority,” said Chief Constable Baggott.

Republicans responsible for the bomb placed under Kerr’s car.

Senior police officers in Ulster have told the Irish Independent that the attack was carried out by a local faction of the Real IRA, centered around a group of experienced ex-Provisionals who sided with the dissidents before the Omagh massacre in August 1998.

The paper claims that the group, based in east Tyrone, operates ‘almost as a freelance outfit and is not affiliated to either of the main RIRA factions - the gang formerly led by Liam Campbell after he split from founder Michael McKevitt, or the dissidents now known as Oglaigh na hEireann’.

Police in the Republic have offered to assist the murder investigation in any way they can.

Martin Callinan, Commissioner of the Garda Siochana police force in the South, offered his sympathy to the Kerr family and the officer’s fellow policemen.

“We in An Garda Siochana stand together with our colleagues in the Police Service of Northern Ireland,” said Commissioner Callinan.

“Our uniforms may be woven from different cloth but the police on this island are bound together by a shared resolve and determination to bring those responsible for this senseless crime to justice.”

Nationalists in Ulster have roundly condemned the attack ahead of the local and Stormont elections next month.

Both Northern Ireland Deputy First Minister Martin McGuinness and his Sinn Fein leader Gerry Adams have branded the killing as an attack on the whole community in Ulster.

Adams said: “Republican heartlands were left seething with anger over this futile murder.

“The revulsion at the killing has affected all sections of the community. I have heard strident condemnations from lifelong republicans who believed the continuing violence was futile.

“The nationalist and republican people of Tyrone, for example, where this action was carried out, or in west Belfast, heartlands, will be angry.

“This isn’t just something which unionists or others will be concerned about.

“The people who I know, and who I have known all my life, the people I have been in touch with overnight, are seething with anger.

“They just see this as a futile action. And some of those are very, very hard-boiled republicans who have been through the hardest part of this struggle over the past 30 or 40 years, who have suffered themselves grievously. They just feel outright anger.”

Read more: Mother begs that son's murder is not in vain

Read more: Northern Irish policeman murdered in dissident bomb attack in Omagh