Police arrested a Spanish man in Belfast today on a European arrest warrant for terrorist offences in Spain.
The 32-year-old man is expected to appear in court later today to face extradition proceedings, police said.
Police did not say if the man was linked to the Basque separatist group Eta, which earlier this month said that the new regional government in Spain's Basque country was a priority target for attack.
In a separate case, Eta member Inaki de Juana Chaos is currently fighting an extradition case from Northern Ireland.
The former leader of Eta's Madrid commando spent 21 years in Spanish jails for crimes including 25 killings, among them the assassination of an admiral and the killing of 12 police officers with a car bomb.
He was arrested in Northern Ireland in November.