Northern Ireland Deputy First Minister Martin McGuinness has said those who murdered Police Constable Ronan Kerr on Saturday are enemies of peace.

Speaking at a news conference in Belfast, after meeting PSNI Chief Constable Matt Baggott, Mr McGuinness condemned the attack.

He said he and Northern Ireland First Minister Peter Robinson had spoken to Taoiseach Enda Kenny and he repeated that nothing would break the peace process.

Mr Kerr was killed by a car bomb in Omagh in Co Tyrone on Saturday.

The bomb which killed Mr Kerr was the size of a lunch box and weighed up to 500g, police said today.

The under-car device was probably detonated using a mercury tilt switch and was housed in a grey plastic container.

The device also contained a timer mechanism which may been used for the safety of the bombers.

Detective Superintendent Raymond Murray believes the device could have been brought into the housing estate anytime between Thursday evening and Saturday afternoon.

25-year-old Ronan Kerr was leaving his home to start work at Enniskillen police station in Co Fermanagh when he was killed.

His mother, Nuala Kerr, urged other young Catholics not to be deterred from joining the PSNI.

She described her son as a wonderful young man who loved his job and appealed to the public for information about his killing.

Mr McGuinness paid tribute to Mrs Kerr, and to the widow of PC Stephen Carroll, the first PSNI officer killed by dissidents.

‘There can be absolutely no doubt that Nuala Kerr is an inspirational woman, just like Kate Carroll is an inspirational woman,’ he said.

‘Our community has been absolutely united over the course of the weekend. We have had a united voice from the community, from church leaders, from civic leaders, from leaders of all the political parties, north and south and, very powerfully, from the Gaelic Athletic Association.

‘The people who murdered Ronan Kerr need to consider all of that, consider how isolated they are, and they need to bring their activities to an immediate end.’

‘My message is very, very simple: those who are perpetrating these acts, those who are killing our people, need to be apprehended.'

Elsewhere, The chairman of Beragh Red Knights GAA Club Gerard Treacy said that the GAA stand 'shoulder to shoulder' with the Kerr family, the PSNI and the entire community in comdemning outright this murder.

Gerard Treacy also said he wanted to send a strong message to the people engaged in this activity; that they have no support in the community and that their actions do not represent the views and feelings of the vast majority of people in Ireland.

No claim of responsibility for attack

Dissident republicans have been blamed for the attack, but no armed group has yet claimed responsibility for the blast.

Speaking on RTÉ's Today with Pat Kenny, Minister for Justice Alan Shatter said the 'barbaric atrocity has caused absolute revulsion' in all communities in Northern Ireland.

He pledged the gardaí would provide every assistance necessary to the PSNI.

The Taoiseach phoned Peter Robinson and Martin McGuinness this morning to discuss the murder of the PSNI officer.

Mr Kenny reiterated that the gardaí will work with the PSNI in its efforts to find those responsible for the killing of Constable Kerr.

The Highfield Close development, where the explosion happened, has been reopened but most residents had, this morning, not yet returned after being evacuated from their homes on Saturday night.

Police are carrying out door-to-door inquiries to gather clues from residents.