South Korea's spy agency said Monday that Kim Jong Gak, a vice chief of North Korea's Ministry of the People's Armed Forces, has been picked to head the military's General Political Bureau, according to parliamentary sources.

According to a lawmaker who attended a closed-door briefing, the agency has intelligence that the bureau's former head Hwang Pyong So, previously regarded as one of leader Kim Jong Un's closest aides, has been dismissed and is currently undergoing ideological education.

The Organization and Guidance Department of the Workers Party of Korea had conducted a rare inspection of the bureau, the first of its kind in two decades, for three months from October.

Hwang, a member of the Presidium of the ruling party, was formerly ranked third in the North's hierarchy behind Kim Jong Un by the country's official media.

However, state-run Korean Central Television on Oct. 8 referred to him as being fifth in command, and last reported his movements on Oct. 13.

South Korea's spy agency, the National Intelligence Service, reported in November that Hwang was being punished for "impure" acts.

The NIS also told parliamentarians Monday that Hwang's deputy Kim Won Hong was similarly dismissed, as were with many other senior members of the bureau.

Since assuming the country's top post in 2011, Kim Jong Un has carried out a series of purges, dismissals and executions in an apparent attempt to tighten his grip on power.