Prosecutors raided the headquarters of the National Intelligence Service of South Korea on Tuesday due to allegations the spy agency used its agents and hired bloggers to influence public opinion ahead of last year's presidential election.
A team of about 25 prosecutors and investigators seized digital files and internal documents from the agency's anti-North Korea psychological warfare team during its search.
The team allegedly posted numerous politically sensitive comments on the internet against the opposition candidate in December's election in order to influence public opinion.
Police said that at least two agents posted the comments earlier this month, but that they could not determine whether they were part of a larger operation.
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Former NIS director Won Sei-Hoon was questioned for 14 hours following the raid about the agency's involvement in the comments posted online. He reportedly denied the charges against him regarding the influencing of public sentiment in favor of the conservative ruling party candidate and claimed the agency's anti-North Korea team was just doing its job of countering Pyongyang's attempts to influence election results.
Won has been barred from leaving South Korea until the results of the investigation are complete.