The Taoiseach has described the British government's decision to begin removing two army watchtowers in South Armagh as "very significant".
Mr Bertie Ahern said the demolition of the observation posts was "an indication of the British government's good faith" and its commitment to implementing the joint declaration issued last week.
Royal Engineers moved in at dawn to begin taking down the watchtowers on the top of Cloghogue Mountain and at Tievecrom, outside Forkhill.
The decision to remove the two posts, from which soldiers have monitored IRA movements for nearly two decades, was announced as part of the normalisation process by the British Prime Minister Mr Tony Blair when he and the Taoiseach Mr published their Joint Declaration last week.
Over the next few months hundreds of tonnes of equipment will be taken from the hilltops and the sites will be returned to "green field" condition and given back to the landowners.
Sinn Féin has been pressing for their removal for years but the decision to go ahead now has provoked protest from the unionist community.
But the security assessment has been taken that the posts can go, following the three others demolished since the autumn of 2001.
When the work has been completed there will still be eight observation posts at six hilltop locations in South Armagh.
Additional Reporting: PA