There have been two further arrests in the Garda inquiry into the 1998 Omagh bombing.
The men, one in his 30s and one in his 40s were detained shortly after 7 a.m. at their homes near the border.
They are being detained under Section 30 of the Offences against the State Act and at Carrickmacross Garda Station and can held without charge for 72 hours.
One man, Colm Muphy, of Co Louth, has so far been convicted in connection with the Omagh bomb attack by the Real IRA that killed 29 people and injured almost 300 others.
Three other men were held for questioning in connection with the blast by Irish detectives last week and subsequently released.
