Belfast (CNN) -- An Irishman has been convicted in Lithuania of attempting to smuggle arms from the Baltic state to paramilitary group the Real IRA.
Michael Campbell, 39, from County Louth in the Republic of Ireland, has been sentenced to 12 years in prison.
He was arrested in Vilnius in January 2008 after an international surveillance operation involving British security services.
Evidence was given during the court case that he had been secretly recorded talking about planting bombs in London.
He was also secretly filmed test-firing weapons in the Lithuanian countryside.
Campbell, who had denied wrongdoing, was Friday found guilty of supporting a terrorist group, illegal possession of weapons and attempted smuggling.
The British government has welcomed the conviction.
Northern Ireland Secretary of State Owen Paterson issued a statement saying it was "another excellent example of what can come from the high levels of cooperation between countries across Europe and beyond in combating terrorism."
Paterson added: "I have no doubt that this will have dealt a blow to RIRA but we are not complacent and we remain determined to do all that we can to bear down on those who are the enemies of the whole community throughout the United Kingdom."
Campbell's brother Liam is one of four men found liable for the 1998 Omagh bombing in a civil case in Belfast.
A Real IRA car bomb exploded in the Northern Ireland town killing 29 people, including a woman pregnant with twins.