South Korea's top intelligence agency has filed a lawsuit against its former head for allegedly leaking confidential information, prosecutors said Wednesday.

The National Intelligence Service took legal action against Kim Man-bok on Tuesday, who headed the agency from 2006 to 2008, for allegedly revealing information about a hotline between South and North Korea.

Kim said at a symposium last week that after the hotline was set up, South Korea reported any messages coming through the hotline immediately to its leaders as coming directly from North Korean leader Kim Jong-il.

The former spy chief later clarified that Roh never spoke to Kim directly by phone.

The North Korean leader held two separate summits with then-South Korean Presidents Kim Dae-jung and Roh Moo-hyun in Pyongyang in 2000 and 2007, respectively. Kim Jong-il died of a heart attack in 2011 and was succeeded by his youngest son, Kim Jong-un.

Under South Korean law, any employee from the NIS wishing to publish or announce content about the agency's duties should first obtain permission from the head of the agency.

The 69-year-old former spy chief co-authored a controversial memoir with Lee Jae-joung and Baek Jong-chun, who served as South Korea's point man on North Korea and presidential security adviser for Roh.

The NIS sought an injunction Monday to halt the sales of the book with the Seoul Central District Court.

The former spy chief was not immediately available for comment.

Kim was also sued in 2011 on suspicions of contributing undisclosed information on the inter-Korean summit to a Japanese monthly magazine, but the indictment was suspended. (Yonhap)