CHEORWON, South Korea — South Korea was dismantling front-line guard posts with dynamite and excavators on Thursday as part of agreements to lower military tensions with North Korea.

The two Koreas last week completed withdrawing troops and firearms from some of the guard posts along their border before dismantling them. The steps are part of the agreements signed in September during their leaders’ summit.

South Korea’s military on Thursday invited a group of journalists to watch the destruction of a guard post with dynamite in the central border town of Cheorwon.

Plumes of thick, black smokes billowed from the site. There were no loud explosions as the journalists were asked to stay hundreds of meters (yards) away from the site. The military later allowed the journalists to watch soldiers and other workers bulldozing another guard post with excavators.

South Korea is dismantling its guard posts mostly with construction equipment because of safety and environment concerns. But it used dynamites for one of the Cheorwon structure because it was located on a high hill where it was difficult to move up excavators, according to Seoul’s Defense Ministry.

North Korea was demolishing its guard posts with explosives, according to South Korean media.

Those guard posts are inside the 248-kilometer (155-mile) -long, 4-kilometer (2.5-mile) -wide border, called the Demilitarized Zone. Unlike its name, it’s the world’s most heavily fortified border with an estimated 2 million land mines peppered inside and near the zone. The area is the scene of numerous violence and bloodsheds since the 1945 division of the Korean Peninsula, and civilians need special government approvals to enter the zone.

The Koreas have agreed to dismantle or disarm 11 of their guard posts each by the end of this month before jointly verifying their works next month. Inside the DMZ, South Korea was known to have run about 60 posts guarded by layers of barbed-wire fences and manned by combat troops with machine guns. North Korea was estimated to have 160 such front-line posts.

Under the September deals, the Koreas are also disarming their shared border village of Panmunjom and clearing mines from another DMZ area where they plan their first-ever joint searches for Korean War dead. They’ve also halted live-fire exercises along the border.

The deals are among a set of cooperation and reconciliation steps the two Koreas have taken since North Korean leader Kim Jong Un reached out to Seoul and Washington early this year with a vague commitment to nuclear disarmament. The fast-improving inter-Korean ties have raised worries among many in South Korea and the United States as a global nuclear diplomacy on the North’s weapons program has produced little progress recently.