An Irishman imprisoned in Lithuania after being convicted of trying to buy weapons for the Real IRA has been freed by an appeal court, his lawyer said.

Michael Campbell, from Co Louth, was arrested in 2008 as part of a sting operation as he allegedly tried to purchase guns and explosives.

He was sentenced to 12 years in prison in 2011 by a court in the Lithuanian capital of Vilnius.

That conviction has now been overturned by a higher court, counsel Ingrida Botyriene said.

"He was acquitted because the court found that what he was accused of was a provocation. It was just an activity of the state security services," she said.

She added that he was glad to be free, almost six years after his arrest.

"It was unexpected, we thought that this case would reach the European Court of Human Rights, we thought it would go a longer distance. Some very serious things are not right in this case but we are happy (he was freed)."

Mr Campbell, from Dundalk, was arrested after an international surveillance operation involving the British secret service, Irish and Lithuanian intelligence services.

He was convicted in October 2011 of supporting a terrorist group, illegal possession of weapons and attempted smuggling.

At the time, Mr Campbell insisted he was set up.

Irmantas Mikelionis, chief prosecutor at the Organised Crime and Corruption Investigation Department of the prosecutor's office, confirmed Mr Campbell had been released.

TDs Maureen O'Sullivan, Clare Daly, Martin Ferris and Éamon Ó Cuív, who had visited Mr Campbell in jail, said they were satisfied with the ruling.

In a statement they said: "It was clear that not only were there serious concerns over his conviction, but that he had spent over five years in poor, overcrowded and inhumane conditions."