Jose Ignacio de Juana Chaos, 54, has already served a jail sentence for his role in 25 murders. Lawyers for the Spanish authorities are seeking to have him returned to Spain to face fresh charges.

Judge Tom Burgess, the Recorder at Belfast's Laganside courts, said: "All courts are more than conscious of the statements and pressures that emanate from many sources outwith the judicial system, but there is no reason to believe that the judicial system of Spain is any less robust in carrying out its duties without fear or favour."

The accused, who was on bail in Belfast, is being sought over the contents of a letter read out at a rally in San Sebastian in August 2008.

The message was allegedly given in his name, with the charge against him heavily dependent on the Basque phrase "aurrrea bolie", which translates literally as "kick the ball forward".

The offence was allegedly committed at a gathering in San Sebastian, Spain, following his release from prison after 21 years for terrorist offences.

He faces the possibility of a two-year jail sentence if convicted of the public justification of terrorist actions which caused humiliation and intensified the grief of victims and their relatives.