A recovery team consisting of university researchers and an army search unit started digging to recover the remains, believed to be buried in several hills in Seoul's Guro ward, the Defense Ministry said.

"We will do some digging today and hope that we can recover some remains," recovery team member Yoo Gyeong-sang said.

The ministry said it has already traced the whereabouts of the remains after gathering testimonies from former soldiers who claim to have moved the bodies to the hills during their service in the air force at the time.

"Why are they here? I can't raise my head because we have to be here now because of the error of the authorities. Those in power should repent," said Lee Myeong-cheol, secretary general of an association of the bereaved families.

The "684 unit," better known as the "Silmido unit" after the local blockbuster film "Silmido" that was based on the story of the commandos, was created by the country's spy agency with the goal of eventually assassinating Kim.

The unit was established on Silmido, a small island off Incheon, in April 1968, three months after 31 North Korean commandos infiltrated South Korea to assassinate then-President Park Chung-hee.

The North Koreans were stopped 300 meters from the presidential office Cheong Wa Dae. Twenty-eight were killed, one was captured and two others were believed to have returned to the North.

But the Silmido unit, consisting of 31 commandos, was disbanded in 1971 after they revolted against the government.