Two men and a woman are in custody today after a joint anti-terrorist operation by Gardai and the PSNI along the border.
The arrests follow a lengthy investigation into the manufacture of home made explosives.
The three were detained around midnight and are suspected of being members of the New IRA Alliance.
A man and a woman, both in their late teens are from south Armagh.
They were detained by the PSNI on the border. In a follow up search, gardai arrested a man in his 40s and he is understood to be from Dundalk.
Officers also uncovered a lock-up premises where it is believed the home made explosives were being mixed.