North Korean Defence Minister Hyon Yong-Chol has been executed by anti-aircraft fire for disloyalty and showing disrespect to leader Kim Jong-Un, South Korea's intelligence agency said Wednesday.

Hundreds of officials watched Hyon's execution on April 30, Han Ki-Beom, the deputy director of the National Intelligence Agency (NIS), told a parliamentary committee, the Yonhap news agency reported.

Hyon, who was appointed to the post of Minister of the People's Armed Forces less than a year ago, was apparently caught dozing off during formal military events and also talked back to Kim Jong-Un on several occasions, Yonhap said.

The Yonhap report was based on a briefing by a ruling Saenuri party lawmaker who attended the parliamentary committee meeting.

Han told the committee that Hyon was executed with anti-aircraft fire -- a method cited in various unconfirmed reports as being reserved for senior officials who the leadership wishes to make examples of.

In North Korea, the defence minister is mainly in charge of logistics and international exchanges. Policy-making is handled by the powerful National Defence Commission and the party Central Military Commission.