The leader of a dissident splinter group calling itself Oglaigh Na hÉireann, who was found guilty of directing terrorism, has previous convictions for membership of the IRA and training people in the use of firearms at an underground firing range, the Special Criminal Court has heard.

Seamus McGrane, 63, from Little Road, Dromiskin in Co Louth, was discovered plotting a bomb attack during the visit of Prince Charles to Ireland two years ago after he was secretly recorded by gardaí discussing explosives and a target of military significance in a pub in Dublin.

He had pleaded not guilty and is to be sentenced next month.

McGrane's defence counsel argued that even though the target was to be "symbolic" and of "military significance" to coincide with the visit of Prince Charles, it was to take place on the opposite side of the country in a graveyard, in the dead of night, with little chance of civilian casualties.

Michael O'Higgins also said his client should not be sentenced to 20 years imprisonment like Michael McKevitt, the first person convicted of the offence.

He said McGrane was directing a different organisation, a splinter group, operating in a different era, which had caused no fatalities.

He also said there should be a correlation between McGrane's sentence and that of his co-accused, Donal Ó Coisdealbha, who was sentenced to five-and-a-half years.

McGrane met Ó Coisdealbha, an IRA operative, a number of times in the Coachman's Inn early in 2015 to plan a bomb attack during the state visit.

However, gardaí had installed listening devices and McGrane was recorded instructing Ó Coisdealbha to "reactivate" "the science graduate" to get advice on explosives.

He told him to contact "motorbike man" to collect the explosives and return the bike, not to dispose of it.

McGrane also told Ó Coisdealbha "the target" was to have "military significance" and referred to someone "coming on the 19th" - the same day Prince Charles arrived in Ireland. He also informed him "he does not like embarrassment".

When gardaí searched McGrane's home and land linked to him in counties Louth and Wexford they found what the judge described as veritable arsenal of weapons and explosives, including improvised rockets, a booster tube and a timing power unit.

Ó Coisdealbha was sentenced to five-and-a-half years in prison last December.

McGrane was also recorded talking about experimenting with the development of explosives and discussed training and swearing people in to the IRA.

He also referred to an attack on Palace Barracks - MI5's headquarters in Northern Ireland and to a bomb on a railway line.

He was found guilty of directing terrorism and membership of the IRA.

The head of the Garda's Security and Intelligence Bureau told the court that McGrane was first convicted of IRA membership in 1976 and that he was also found at an underground IRA shooting range in Stamullen in Co Meath in 1999 training people to use firearms, for which he was sentenced to four years in prison.