Chief Constable Matt Baggott has met senior politicians this morning to discuss the weekend murder of Catholic police officer Ronan Kerr.

Mr Baggott said that he would not be deflected from "doing the things that matter".

"Our commitment remains solid," he added.

The 10am summit followed the murder of the 25-year-old constable who was killed by a booby-trap bomb which exploded under his car in Omagh on Saturday.

This afternoon, it was revealed that the bomb was inside a plastic box and probably set off by a tilt switch.

Detective Superintendent Raymond Murray told BBC NI that he believed it was planted some time between Thursday evening and when it exploded on Saturday afternoon.

Chief Supt Murray said components of the bomb had been recovered and the device was up to 500g in weight.

Earlier today, the outgoing First Minister Peter Robinson, the former Deputy First Minister Martin McGuinness and the outgoing Justice Minister David Ford met with the Chief Constable.

The briefing was just hours after the dead policeman's mother Nuala Kerr called on Catholics to keep joining and supporting the police, saying she did not want her son to die in vain.

Speaking on Morther's Day, Mrs Kerr said: "It's a sad day for our community. Ronan was a valued member and he had so much to offer."

Justice Minister and Alliance party Leader, David Ford (pictured here with Matt Baggott) said politicians should "follow through on the lead given so strongly by Ronan Kerr's mother".

He added: "We have to stand united and overcome division."

The killing has already been widely condemned with Mr Ford's colleague, the Alliance Justice Spokesperson Stephen Farry commenting: "The thoughts and prayers of people right across the community in Northern Ireland will be with the family of this brave officer.

"This was a most despicable and cowardly attack. It is more than just an attack on an individual police officer but an attack on the entire community.

"In turn, the entire community will be united in rejecting and thwarting those men of violence who are seeking to drag us back to the dark past from which society is emerging," he said.

"If anybody has any information about this murder then I would urge them to contact the police."

The murder victim is the second PSNI officer to be killed by the terrorists since it replaced the RUC as part of post Peace Process policing reforms.

In March 2009, Police Constable Stephen Carroll was shot dead as he answered a 999 call in Craigavon.

Two days earlier, two soldiers - Sappers Mark Quinsey and Patrick Azimkar - were gunned down outside their barracks in Antrim, as they collected a pizza delivery.

Later, a PSNI officer and well-known GAA player, Peadar Heffron, was seriously injured when a device exploded under the driver's seat of his car in January 2010.

Police Federation Chairman, Terry Spence, condemned the murder of the constable as cowardly and counterproductive.

"We will never be deterred by terrorism from doing our duty and serving the whole community," he said.

"On behalf of my members I call upon the community to help us bring these murderers to justice.

"Wherever officers serve they must be extremely vigilant about their personal security both on and off-duty."

Prime Minister David Cameron also expressed his sympathy: "I utterly condemn the murder of a young police officer today in Omagh, who had dedicated himself to serving the entire community of Northern Ireland.

"Our thoughts and prayers go out to his family and his friends. This is a terrible tragedy for all who knew him and served with him, and for a town that had already suffered so much.

"Those who carried out this wicked and cowardly crime will never succeed in dragging Northern Ireland back to a dark and bloody past.

"Their actions are rejected by the overwhelming majority of people from all parts of the community.

"I know that the Chief Constable will not rest until the perpetrators have been brought to justice," he said.

The Taoiseach, Enda Kenny, said it was a "heinous and pointless act of terror".

"Those who carried it out want to drag us back to the misery and pain of the past. They are acting in defiance of the Irish people," he said.

The Sinn Fein MP for West Tyrone Pat Doherty has said that those responsible for the murder of Ronan Kerr in no way represent the views, opinions or political aspirations of republicans in the county.

"There is no cause served by this action. No explanation can be offered. As a lifelong republican, as an elected representative, I can say that this act cannot be claimed in the name of republicanism, the people of Tyrone, or the people of Ireland.

"The only purpose behind these groups appears to be to carry out sporadic acts of violence as either a cover for their criminal activity or crudely to demonstrate that they can bomb and kill.

"The groups that perpetrate these actions acknowledge that they have little support and no strategy. They have no regard for the community. They have no regard for the wishes of the Irish people," he said.

Against this backdrop, the PSNI have this morning been treading carefully as they undertake a security alert in Lurgan after a warning that a bomb had been left on waste ground at a disused factory in the town.

Searches are being carried out at the old Glendinning factory. Police say a number of homes in the nearby Allen Hill Park area may have to be evacuated.

See: Bombed Officer Looses Leg

See: Three Held Over PSNI Death

(BMcC/GK)