Prosecutors have secured evidence that the National Intelligence Service illegally spied on the head monk of a Buddhist temple in Seoul in an attempt to oust him for criticizing the government of then-President Lee Myung-bak, officials said Thursday.

Prosecutors plan to question the spy agency chief at the time, Won Sei-hoon, about suspicions that he ordered illegal surveillance on Ven. Myungjin, the then-head monk at the Bongeunsa temple in southern Seoul, after the monk publicly lashed out at the Lee administration.

Prosecutors have obtained testimonies quoting Won as saying during a meeting of NIS officials in July 2010 that the monk was a pro-North Korean leftist and it would be a dereliction of duty if the intelligence agency did nothing about him, officials said.