The Seoul High Court on Monday sentenced Won Sei-hoon, who served as director of South Korea's National Intelligence Service (NIS) from 2009 to 2013, to three years in jail "for activities against a particular (opposition) political party," according to the Yonhap news agency.

It also cited the ruling as saying that Won, 64, had neglected "the duty of political neutrality and meddled in the political-decision making process allowed to voters."

The charges against him are related to a national smear campaign against opposition candidate Moon Jae-in, who Park Guen-hye narrowly defeated in the December 2012 presidential election. Specifically, it found that he had directed NIS agents to post thousands of comments in online forums, supporting Park while disparaging Moon.

Previous suspended sentence

In September, a district court had handed Won a two-and-a-half year suspended sentence, ruling that while there was clear evidence of wrongdoing, there was not enough proof that he had intended to directly influence the outcome of the election.

However, the High Court on Monday found that his crime was serious enough to warrant a custodial sentence.

"It is fair to say Won had the intention to intervene in the election," Judge Kim Sang-hwan said.

As he was led out of the court, Won, who stepped down as spy chief in March 2013, insisted that his actions were motivated by his determination to work "for the safety of my country and its people."

It's not clear if or how the online campaigning affected the election, but President Park has denied benefitting from the efforts of NIS workers to sway the vote.

This is just the latest scandal to hit the spy agency, which has implemented numerous reforms and gone through two name changes in a bid to win back the confidence of the general public in South Korea.

pfd/rg (Reuters, AFP, AP)