Man in custody over Omagh bombing
Seamus Daly was arrested in Newry on Monday.
Up to 29 people, including a woman pregnant with twins, died in the Real IRA car bombing in the Tyrone town on August 15.
The man was arrested by detectives from the PSNI. He is being questioned by police in Antrim.
The attack is considered one of the worst atrocities of the Troubles. No-one has been convicted of carrying out the bombing in a criminal court.
However, relatives of some victims brought a civil action against five men they claimed were responsible, including Mr Daly. The court ruled that the men were responsible for the attack. Daly and another man were later ordered to pay £1.6m damages.
Last year, families of victims vowed to take the British government to court after branding its decision to rule out a public inquiry into the attack as a feeble bid to hide from the truth.
Relatives made the pledge to take judicial review proceedings after Northern secretary Theresa Villiers said there were not sufficient grounds to justify an independent probe.
There have been long-standing allegations that intelligence and investigative failures by authorities on both sides of the border allowed the bombers to carry out the crime and get away with it.
