In the last year South Korean troops have found and removed 168 land mines. Since 1998, when South Korea launched a major effort to remove Korean War (1950-53) era landmines, over 68,000 have been found and removed. This mine clearing campaign is part of a larger plan to eventually remove all landmines from South Korea and North Korea.
While landmines are technically "banned" weapons, there are still plenty in use and one of the most mined areas is Korea. The Mine Ban Treaty came into force in 1999, but 42 countries did not agree to the ban on the production, stockpiling, and use of antipersonnel mines. Countries who opted out include China, India, Pakistan, Russia, South Korea, and the United States. This list includes the major producers of landmines, as well as many of those still using landmines.
South Korea has about a million landmines emplaced along the DMZ between north and south Korea. The U.S. and South Korea have another two million or so mines in storage, in case North Korea tries to invade again (as it last did in 1950). North Korea won't say how many mines it has planted but it's probably at least several hundred thousand.
South Korea has to replace mines as they get too old to still work, and in the last decade they have been doing this with a new generation of command (by wire or wireless) detonated mines. Many of the more recent mines South Korea has stockpiled are of the self-destruct (a certain amount of time after planted) variety. South Korea has been making plans for clearing all the mines it has planted over the years, largely because it appears that the communist government of North Korea will collapse soon, eliminating the need for the DMZ and all those mines.
Despite these mine clearing efforts, there is no quick way to clear all landmines. That’s because many of those planted during the Korean War were not recorded or records of these mine fields were destroyed during combat or lost after the war. Even mines with a recorded location can be shifted by landslides or heavy rains. Old mines and unexploded bombs and shells will continue to show up for decades. Such has been the case in the United States, where explosives from the Civil War (1861-65) still get found. Similarly, in Europe the tens of millions of mines and unexploded munitions are regularly being encountered by farmers or construction crews.