A former National Intelligence Service official was called in by prosecutors on Thursday for further questioning over his role in an online smear campaign led by the spy agency from 2009-2013, a prosecution office said. 

Lee Jong-myeong, a former senior NIS official who headed the psychological warfare division, appeared at the Seoul Central District Prosecutors' Office in the afternoon.

Lee refused to answer any questions from reporters, only saying that he will "earnestly comply with the interrogation."

Lee has already been convicted of political interference in violation of NIS and election laws, along with former NIS chief Won Sei-hoon who received a four-year jail term for masterminding the whole scheme. Both are awaiting the top court's decision. 

Prosecutors reopened the investigation into the case after an internal NIS probe found documents that suggest the spy agency ran 30 such cyberteams and spent billions of taxpayer money to pay civilians and NIS retirees hired to write disparaging Internet comments about liberal figures. 

On Tuesday, they arrested Min Byung-joo, who worked in Lee's unit, on charges of loss of state funds, as he was in charge of managing the payroll.

The cyberteams are believed to have carried out an all-out smear campaign against then liberal candidate Moon Jae-in, aimed at swaying votes in favor of his contender Park Geun-hye from the conservative ruling party before the 2012 election. Park won the vote by a thin margin.

The prosecution has been widening the high-profile investigation since President Moon Jae-in took office in May, following the ouster of his predecessor, Park Geun-hye, over a massive corruption scandal. (Yonhap)