North Korea has executed its defence chief on treason charges, Seoul's National Intelligence Service (NIS) has told South Korean politicians.

The execution appears to be the latest of a series of high-level purges since Kim Jong-un took power after his father's death in 2011.

NIS 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.

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The office of another lawmaker, Lee Cheol-woo, released similar information about the NIS briefing.

Hyon, who spoke at a security conference in Moscow in April, was said to have shown disrespect to Kim by dozing off at a military event, media said, citing the agency briefing.

North Korea has not commented on the reports.

The execution comes after South Korea's spy agency said late last month that Kim had ordered the execution of 15 senior officials this year as punishment for challenging his authority.

Volatile internal politics

"North Korean internal politics is very volatile these days," said Michael Madden, an expert on the North Korean leadership and contributor to the 38 North think-tank.

"Internally, there does not seem to be any respect for Kim Jong-un within the core and middle levels of the North Korean leadership."

In 2013, Kim purged and executed his uncle, Jang Song-thaek, once considered the second most powerful man in Pyongyang's leadership circle, for corruption and committing crimes damaging to the economy, along with a group of officials close to him.

Pyongyang's military leadership has been in a state of perpetual reshuffle since Kim took power.

Hyon, a little-known general, was promoted to the rank of vice marshal of the North Korean army in 2012.

The South Korean spy agency told politicians that Ma Won-chun, known as North Korea's chief architect of new infrastructure under Kim, was also purged, local media reported.

Source: Agencies