North Korean leader Kim Jong Un executed his defense chief for sleeping during a meeting and talking back to the young leader, South Korea's spy agency told lawmakers Wednesday, citing what it called credible information.

National Intelligence Service officials told a closed-door parliamentary committee meeting that People's Armed Forces Minister Hyon Yong Chol was killed by anti-aircraft gunfire with hundreds watching at a shooting range at Pyongyang's Kang Kon Military Academy in late April, according to lawmaker Shin Kyoung-min. Shin attended the briefing.

The office of anther lawmaker Lee Cheol Woo released similar information about the NIS briefing.

The NIS didn't tell lawmakers how it got the information, only that it was from a variety of channels and that it believed it to be true, Shin said. The agency wouldn't comment when contacted by The Associated Press. South Korea's spy agency has a spotty record of tracking developments in North Korea. Information about the secretive, authoritarian state is often impossible to confirm.

Since taking power upon the death of his dictator father in late 2011, Kim has orchestrated a series of purges in apparent efforts to bolster his grip on power. Analysts are split on whether the bloody power shifts indicate a young leader in firm control, or someone still struggling to establish himself. The most notable purge was in 2013 when Kim executed his uncle and chief deputy, Jang Song Thaek, for alleged treason.

Koh Yu-hwan, a North Korea expert at Dongguk University in Seoul, said Kim Jong Un appears to be using purges to keep the military old guard in check as they pose the only plausible threats to his rule. Koh said Kim could be resorting to a "reign of terror" to solidify his leadership but that would eventually have only a limited effect if he fails to produce breakthroughs in resolving the country's economic woes.

Last month, spy officials told lawmakers that North Korea executed 15 senior officials accused of challenging Kim's authority.

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Associated Press writer Kim Tong-hyung contributed to this report.