Shocking atrocity: police and firemen at the scene of the Omagh bomb

An FBI spy who infiltrated dissident republican ranks warned that Omagh had been identified as a potential target weeks before the town was bombed, the High Court has heard.

Lawyers for the father of a young man killed in the Real IRA atrocity claimed emails sent by David Rupert provided an opportunity to carry out surveillance on "people of interest".

Michael Gallagher is challenging the British Government's refusal to hold a public inquiry into the August 1998 attack.

His son Aiden was among 29 people, including a woman pregnant with twins, who died in the massacre.

The case centres on claims that a range of intelligence from British security agents, MI5 and RUC officers could have been drawn together to prevent the bombing.

As the hearing got underway Hugh Southey QC, for Mr Gallagher, referred to emails from Mr Rupert, a US trucking boss-turned FBI spy said to have infiltrated the Real IRA and Continuity IRA during his time in Ireland.

Correspondence sent weeks before the strike on Omagh names a man who allegedly suggested reduced warning times for bombs to increase the risk, as well as the need for "more bangers" and to have "a few more British going home in boxes".

The court heard Omagh was identified as a potential target by both Mr Rupert and in an anonymous call to police on August 4 - 11 days before the attack.

Mr Southey stressed those strands must be viewed together rather than analysed in isolation.

"One needs to look at whether or not this material demonstrated real and immediate risk, and whether the actions taken were reasonable," he said.

"The problem is, on the open evidence, nobody links (the) Rupert (emails) to the anonymous call.

"Had they done that one would at the very least have reached the conclusion there was an increased desire on the part of dissident republicans to carry out fatal attacks, and Omagh was being mentioned, not just once but twice, as a potential target."

Mr Gallagher launched his legal action after former Northern Ireland Secretary of State Theresa Villiers rejected calls for a public investigation back in September 2013.

She decided instead that a probe by Police Ombudsman Michael Maguire was the best way to address any outstanding issues surrounding the outrage.

In October 2014 Dr Maguire published a report where he found RUC Special Branch withheld some intelligence information from detectives hunting the bombers.

No one has ever been convicted of carrying out the attack.

The challenge had been delayed due to issues over holding partially closed hearings to protect national security.

Mr Southey advanced the case on behalf of Mr Gallagher before proceedings continue in private session.

"Whatever one makes of the Rupert material on its own, if one links it with other material suggesting dissidents were generally well equipped and material suggesting Omagh might be a target, one might have expected greater action to be taken," the barrister submitted.

"The basic point I'm making is Rupert, on the face of it, identified both reason to carry out surveillance operations and an opportunity to carry out surveillance operations by identifying people of interest.

"However, if these surveillance operations were to be of maximum impact one needed full information."

The hearing, which is listed for five days, continues.

Belfast Telegraph