People pose for photo during an unveiling ceremony of a monument in Hongdo, Sinan County, in this photo provided by the unification ministry, June 3. Yonhap

South Korea on Monday unveiled another monument on a small southwestern island, hoping for the safe return of South Korean high school students abducted by North Korea in the late 1970s.

Four high school students were kidnapped by North Korean agents on Hong Island, off the southwestern coast, between 1977 and 1978, and they have yet to return home. A similar monument was set up on the southwestern island of Seonyu last month to wish for the repatriation of another teen abducted in 1977.

The ministry held a ceremony Monday to unveil the monument dedicated to these abductees, bringing together family members of the victims as well as Vice Unification Minister Moon Seoung-hyun.

The monument was installed to express South Korea's commitment to never forgetting the abductees and to raise public awareness for their return, it said.

Currently, six South Koreans are being detained in North Korea, including three missionaries — Kim Jung-wook, Choi Chun-gil and Kim Kook-kie — whose whereabouts and fates are unknown.

Separately, 516 South Koreans have yet to return home among an estimated 3,835 people who were kidnapped by North Korea after the Korean War, according to government data. (Yonhap)