A man is being questioned by detectives investigating the Omagh bombing, which left 29 people dead, one of them a pregnant mother expecting twins.
He was detained in Newry, Co Down police said tonight.
The suspect was taken to the serious crime suite in Antrim for questioning by the PSNI’s Terrorist Investigation Unit.
No one was ever been convicted of the August 15, 1998 atrocity which was carried out by the Real IRA.
The device exploded on a busy Saturday afternoon while parents were out shopping with their children.