Na, now 80 years old, was indicted in 1985 on charges of violating the National Security Law by illegally visiting North Korea and drew a 15-year prison term the following year.

The former entrepreneur was accused of acting as a resident spy after his North Korea visit and collecting military secrets.

He was released from prison in January 1998 after spending 13 years behind bars.

In March 2015, Na requested a retrial, arguing that he had never received espionage instruction and training from North Korea, and was forced to make false confessions during illegal detention and torture by investigators.

He was acquitted of his espionage charges in August 2017 and paid 950 million won in state compensation for his wrong detention.

"The state has a duty to protect the basic human rights of the people but became a violator of the basic rights in Na's case," said the Seoul court, ordering additional state compensation for the victim. (Yonhap)