South Korea's top court upheld a lower court ruling that said the state spy agency should disclose information regarding South Korean soldiers' alleged massacre of civilians during the Vietnam War.

The Supreme Court's decision on Friday comes after the progressive Lawyers for a Democratic Society requested that the National Intelligence Service(NIS) provide documents on the alleged killing of some 70 Vietnamese civilians in 1968.

The lawyers' group filed an administrative suit after the NIS refused to reveal details from the then-Korea Central Intelligence Agency's interrogation of three Vietnam War veterans linked to the allegations.

Even after the group partially won the first case in November 2017, the NIS continued to refuse, citing that some of the information was classified.

A separate case is underway after a Vietnamese woman filed a suit against the South Korean government regarding the allegations.