Police were today questioning a man arrested in Belfast city centre as part of a probe into Basque separatist activity.
In a joint operation with Spanish Police, officers from Police Service of Northern Ireland's (PSNI) Serious Crime Branch detained the 40-year-old suspect yesterday evening under terrorism legislation.
He is being held in the province's Antrim Serious Crime suite.
No other details were given about the arrest.
A PSNI spokesman said: "A 40-year-old man has been arrested under terror legislation in a joint operation between PSNI Serious Crime Branch and Spanish Police.
"The man was arrested in Belfast city centre and has been taken to Antrim Serious Crime suite for questioning."