VILNIUS (AFP) – A man suspected of trying to buy arms in Lithuania for an Irish Republican Army splinter group that has returned violently to the spotlight will finally face trial in the Baltic state Tuesday.

Michael Campbell, a 36-year-old Irish citizen who is a brother of a senior Real IRA commander, has been behind bars for 19 months since being snared in the Lithuanian capital Vilnius.

Prosecutors in the ex-Soviet republic accuse him of attempting to obtain weapons illegally and aiding a terrorist organization. The crimes carry sentences of up to eight years, and 20 years, respectively.

It is not clear how long the trial will last.

His lawyers claim the case is groundless.

''The defence regards as insufficient the evidence produced by the prosecution,'' one of Campbell's Lithuanian lawyers, Ingrida Botyriene, told AFP. She refused to elaborate.

Campbell was arrested in Vilnius in January 2008 while meeting with an undercover Lithuanian agent who reportedly offered him weapons. His wife, Fiona Duffy, was also detained but released four months later.

His supporters claim Campbell -- who reportedly has a criminal record for tobacco-smuggling -- was in Vilnius to buy cigarettes and was set up by British intelligence working with the Lithuanians.

One group, the Irish Republican Prisoners Welfare Association, dubs him a ''hostage'' and a ''prisoner of war''.

His supporters also complain he is barred from contacting his family, is being held with three inmates who do not speak English and regularly take drugs, and that the cell lights are switched off as part of Lithuania's anti-recession drive.

The Real IRA is a splinter group of the Provisional IRA, once the main Catholic militant organization opposed to British rule in Northern Ireland.

Campbell's brother Liam was one of four Real IRA leaders found liable in June for Northern Ireland's deadliest single attack, the August 1998 bombing in the town of Omagh that killed 29 people.

The blast failed to derail the Good Friday peace accord of April 1998 that ended most of Northern Ireland's ''Troubles'', three decades of sectarian strife between Catholics and pro-British Protestants.

The Real IRA broke with the mainstream movement in 1997 over the latter's support for the peace drive.

The Real IRA returned to the spotlight in March when it claimed a shooting at a British army barracks in Northern Ireland which killed two soldiers and seriously wounded two other soldiers and two pizza delivery men.

Liam Campbell, 46, is also wanted in Lithuania, which as a member of the European Union since 2004 can request fast-track extradition.

He is locked in a legal battle, after having been arrested in Ireland in January on a Lithuanian warrant, released pending a decision, then detained in May in Northern Ireland, where he remains in custody.