SEOUL, South Korea — North and South Korean troops began removing some of the land mines planted at their heavily fortified border on Monday, Seoul officials said, in the first implementation of recent agreements aimed at easing their decades-long military standoff.

The demining comes amid resumed diplomacy over North Korea’s nuclear weapons program after weeks of stalemated negotiations. U.S. Secretary of State Mike Pompeo is to visit Pyongyang, North Korea’s capital, this month to try to set up a second summit between President Donald Trump and North Korean leader Kim Jong Un.

Under deals signed by their defense chiefs on the sidelines of a September summit between Kim and Moon, the demining of the Joint Security Area is part of a broader step to “disarm” the zone and turn it to a “place for peace and unity.”

The Koreas will likely end up pulling out a small portion of an estimated 2 million mines littered inside and near the 155-mile-long Demilitarized Zone.

On Monday, South Korean army engineers with demining equipment were deployed to the border village of Panmunjom and Arrow Head Hill, where the Koreas plan their first joint searches for soldiers killed during the 1950-53 Korean War.

At Arrow Head Hill, some of the war’s heaviest fighting took place over a strategically important hilltop position.

The troops began removing mines on the southern part of the two sites. Later Monday, the South Korean military detected North Korean soldiers engaged in what it believed was demining on the northern part of the sites, a South Korean defense official said on condition of animosity, citing department rules.

The official refused to provide more details. North Korea's state media didn't immediately confirm its reported demining.

Experts believe the South Korean and U.S. militaries have planted about 1-1.2 million mines south of the DMZ while North Korea has put about 800,000-1 million mines on its side. It’s not known how many mines are at Panmunjom and Arrow Head Hill, but military commentator Lee Illwoo said the Koreas would be able to clear tens of thousands at most.

At Arrow Head Hill, Seoul officials believe there are remains of about 300 South Korean and U.N. forces, along with an unspecified number of Chinese and North Korean remains.

The Korean War left millions dead or missing, and South Korea wants to expand joint excavations with North Korea for remains at DMZ areas.

Mines dislodged by flooding and landslides have occasionally caused deaths in front-line areas in South Korea. In 2015, a land mine blast blamed on North Korea maimed two South Korean soldiers and pushed the Koreas to the brink of war.

In this on Sunday, Sept. 30, 2018 photo, military guard posts of North Korea, right top, and South Korea, left bottom, are seen in Paju, at the border with North Korea, South Korea. Seoul on Monday, Oct. 1, 2018, says South Korea has begun clearing mines from two sites inside the heavily fortified border with North Korea under a package of tension-reduction deal between the rivals. (Kim Do-hoon/Yonhap via AP)
In this on Sunday, Sept. 30, 2018 photo, military guard posts of North Korea, right top, and South Korea, left bottom, are seen in Paju, at the border with North Korea, South Korea. Seoul on Monday, Oct. 1, 2018, says South Korea has begun clearing mines from two sites inside the heavily fortified border with North Korea under a package of tension-reduction deal between the rivals. (Kim Do-hoon/Yonhap via AP)

The agreement to clear mines, the first such effort since the early 2000s, was among a package of tension-easing deals struck by the Koreas' defense chiefs on the sidelines of a leaders' summit last month in Pyongyang.

Aiming to reduce conventional military threats, they also agreed to remove 11 front-line guard posts by December and set up buffer zones along their land and sea boundaries and a no-fly zone above the border to prevent accidental clashes.

Moon said Monday the military deals will “end all hostile acts on land, sea and sky between South and North Korea.” In a speech marking South Korea’s 70th Armed Forces Day, Moon also called for a stronger national defense, saying “peace can continue only when we have power and are confidant of protecting ourselves.”

Moon, a liberal who aspires to improve ties with North Korea, is a driving force behind U.S.-North Korean nuclear diplomacy. Critics of his engagement policy have lambasted the recent inter-Korean military deals, saying a mutual reduction of conventional military strength would weaken South Korea's war readiness because the North's nuclear program remains largely intact.

"I think it's the worst-ever South-North Korean agreement that made a concession in our defense posture before (North Korean) denuclearization is achieved," Shin Wonsik, a former vice chairman of the South's Joint Chiefs of Staff, said last week.

Many experts say the fate of inter-Korean deals can be affected by how nuclear negotiations go between the United States and North Korea. Past rapprochement efforts were often stalled after a standoff over the North’s nuclear ambitions intensified.

After provocative tests of three intercontinental ballistic missiles and a powerful nuclear weapon last year, North Korea entered talks with the United States and South Korea earlier this year, saying it's willing to deal away its expanding nuclear arsenal.

The nuclear diplomacy later came to a standstill amid disputes over how sincere North Korea is about disarmament. But Trump, Pompeo and other U.S. officials have recently reported progress in denuclearization discussions with the North. Pompeo is to make his third trip to North Korea soon.

Meanwhile, on Monday, South Korea held a ceremony marking the recent return of the remains of 64 South Korean soldiers missing from the Korean War. They were earlier found in North Korea during a joint 1996-2005 excavation project between the United States and North Korea.

Forensic identification tests in Hawaii confirmed they belong to South Korean war dead, according to Seoul’s Defense Ministry.

Associated Press writer Kim Tong-hyung contributed to this report.