At Panmunjom, the Koreas are to spend 20 days clearing mines before withdrawing troops, weapons and guard posts in the area over the next five days.
According to the South Korean military, the removal operations took place at two sites inside the Demilitarized Zone: the Joint Security Area at the border village of Panmunjom and Arrow Head Hill in mountainous Gangwon Province. Troops will remain there - but will be unarmed.
The North has for decades demanded that the USA formally declare the end of the 1950-53 conflict that was halted only with an armistice, saying an official end to the war would ease tensions on the flashpoint peninsula.
A spokesman said the operation had begun on both sides, though this was not confirmed by the North.
Experts believe the South Korean and US 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. A 2015 DMZ mine explosion blamed on North Korea that maimed two South Korean soldiers pushed the rivals to the brink of an armed conflict.
The Associated Press reports that the South Korean and USA militaries have set one million to 1.2 million landmines south of the DMZ.
Military officials have predicted that once the disarming measure is implemented, the JSA will look similar to what it had been like before the 1976 axe murder incident, when rank-and-file guard posts were banned from carrying heavy firearms - even pistols.
South Korea would find itself more vulnerable to North Korean infiltration and assault via land routes, while North Korea would worry about front-line soldiers and residents escaping to the South more easily, Lee said.
The troops will try to remove mines on the southern parts of the two sites while North Korea is required to do the same on their northern sides.
Moon, a liberal who aspires to improve ties with North Korea, is a driving force behind U.S.
Meanwhile, on Monday, South Korea held a ceremony marking the recent return of remains of 64 South Korean soldiers missing from the Korean War.
Seoul's Defense Ministry says North Korea is expected to do the same on Monday. He also said the north is committed to helping maintain "long lasting peace and prosperity" on the peninsula.
The summit was the third this year between the leaders, following a rapid thaw in relations.
The North entered talks with the United States and South Korea earlier this year, saying it is willing to negotiate away its advancing nuclear arsenal. But it said the U.S.is "trying to subdue" it through sanctions - a clear call for Washington to lift sanctions if it wants further progress in their stalled nuclear negotiations. The remains of a large number of Chinese and North Korean soldiers are also likely there. They were earlier found in North Korea during a joint 1996-2005 excavation project between the United States and North Korea.