Northern Ireland Secretary John Reid said workers began dismantling towers on Sturgan Mountain and Camlough Mountain in the so-called "bandit country" of South Armagh, a region of high Irish Republican Army support bordering the Republic of Ireland.
Demolition of a lookout post at Newtownhamilton, another South Armagh border town, and an army base at Magherafelt, a predominantly Roman Catholic town in the province's center, would begin this week, Reid said.
"Our aim is to secure as early a return as possible to normal security arrangements," he said.
Reid also said Britain and Ireland would not seek extradition of IRA members for offenses committed before April 10, 1998, the date of the Good Friday peace accord. That would allow about two dozen IRA suspects to return to Northern Ireland without fear of prosecution.
Ulster Unionist leader David Trimble announced that his Protestant party's three Cabinet ministers in the Northern Ireland unity government resumed their offices Wednesday.
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They resigned last week to protest the IRA's refusal to disarm. Had they not returned, Thursday was the deadline for the government to be suspended or collapse.
The next, more contentious step comes next week, when Trimble, a Nobel Peace Prize laureate, is expected to seek re-election as leader of the government.
He needs majority support from both the Protestant and Catholic blocs in Northern Ireland's legislature. While Catholics have pledged their support, Protestant lawmakers are almost evenly divided over whether to sustain an arrangement that includes the IRA-linked Sinn Fein party.
On Tuesday, international disarmament officials confirmed that the IRA had put a substantial amount of weapons "beyond use."
Security officials have estimated the IRA possesses more than 100 tons of weapons in secret bunkers throughout the Republic of Ireland, much of it smuggled from Libya in the mid-1980s.
Chief Constable Ronnie Flanagan, commander of Northern Ireland's police force, said it was too early to declare that the IRA would never take up arms again.
But "we are certainly the closest yet, in my estimation, to saying that the war waged by the Provisional IRA is over," Flanagan said, using the outlawed group's full name.
Some anti-British militants, however, predicted that even more IRA members would join dissident groups committed to mounting more bomb and gun attacks in pursuit of the IRA's traditional aim - the abolition of Northern Ireland as a Protestant-majority state. Since 1970 IRA violence has claimed more than 1,800 lives.
"Only one secion of the IRA is disarming," said Joe Dillon, a senior supporter of a splinter IRA group nicknamed the Real IRA, formed after the IRA's 1997 cease-fire. The Real IRA was behind the deadliest attack in the past three decades of conflict, a 1998 car-bomb attack on the town of Omagh that killed 29 and wounded more than 330.
And in an apparent sign that the group remains active, two men were arrested Wednesday at a police checkpoint in possession of a submachine gun. Flanagan said they were Real IRA suspects.
Outlawed anti-Catholic groups have shown no sign of following the IRA's lead on disarmament. Two of those groups, the Ulster Defense Association and Loyalist Volunteer Force, earlier this month had their cease-fires declared invalid by Britain because of recent attacks on Catholics.
But Sinn Fein president Gerry Adams said he wasn't concerned about disarming the Protestant groups.
"There is no big demand from within the broad Sinn Fein constituency for the loyalists to be put through hoops over the question of guns, we simply want them to stop using their guns and we simply want them to stop using their bombs," he said in Dublin.
By Shawn Pogatchnik
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