SEOUL (AFP) - A former senior official of South Korea's spy agency was detained Tuesday (Oct 17) over allegations that he led efforts by the organisation to undermine critics of the country's previous conservative governments.

Choo Myeong Ho, a former department head at the National Intelligence Service (NIS), is suspected of directing a string of operations to monitor and undermine high-profile figures and celebrities critical of then president Lee Myung Bak and now ousted president Park Geun Hye.

Choo was taken into emergency custody on charges of abuse of authority and political interference in violation of NIS law, the Seoul Central District Prosecutors' Office said, adding it will request a court warrant to arrest him formally.

He is also accused of taking the lead in smear campaigns against the leftist-leaning current Seoul mayor Park Won Soon, who triumphed over a conservative rival in 2011 by-election and emerged as a potential presidential candidate.

A NIS internal investigation team has filed complaints with prosecution authorities, calling for Choo to face criminal charges.

The spy agency has been conducting a house-cleaning under the government of new President Moon Jae In, who took office in May.