SEOUL (AFP/REUTERS) - 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 on Wednesday.Hundreds of officials watched Mr Hyon’s execution on April 30, Mr Han Ki Beom, the deputy director of the National Intelligence Agency (NIS), told a parliamentary committee in a briefing on Wednesday, the Yonhap news agency reported.

Mr Hyon, who spoke at a security conference in Moscow in April and was appointed to the post of Minister of the People’s Armed Forces less than a year ago, was said to have shown disrespect to Mr Kim by dozing off at a military event, the Seoul lawmakers said, citing the agency briefing.

Mr Hyon was believed to have voiced complaints against Mr Kim and had not followed his orders several times, according to the lawmakers. He was arrested late last month and executed three days later without legal proceedings, the NIS said.

The Yonhap report was based on a briefing by a ruling Saenuri party lawmaker who attended the parliamentary committee meeting. It was not clear how the NIS received the information and it is not possible to independently verify such reports from within secretive North Korea.

Mr Han told the committee that Mr 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. Mr Han said hundreds of people witnessed the execution, which was believed to have been carried out with an anti-aircraft gun at a military academy in northern Pyongyang.

The South Korean spy agency told lawmakers that Mr Ma Won Chun, known as North Korea’s chief architect of new infrastructure under Mr Kim, was also purged, local media reported. Mr Ma had also once served as vice-director of the secretive Finance and Accounting Department in the ruling Workers’ Party and, up until recently, was effectively the regime’s money man. He had been regularly photographed alongside Mr Kim in state propaganda images, but had not made any reported appearances since November last year.

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

In all, around 70 officials have been executed since Mr Kim took over after his father’s death, Yonhap news agency cited the NIS as saying.

“North Korean internal politics is very volatile these days,” said Mr 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,” he added.

“There is no clear or present danger to Kim Jong Un’s leadership or stability in North Korea, but if this continues to happen into next year, then we would seriously have to start looking at a contingency plan for the Korean Peninsula”.

The lawmakers said Mr Hyon was executed at a firing range at the Kanggon Military Training Area, 22km north of Pyongyang.The United States-based Committee for Human Rights in North Korea said last month that, according to satellite images, the range was likely used for an execution by ZPU-4 anti-aircraft guns in October. The target was just 30m away from the weapons, which have a range of 8,000m, it said.

“The gut-wrenching viciousness of such an act would make ‘cruel and unusual punishment’ sound like a gross understatement,” the group said on its website. “Given reports of past executions this is tragic, but unfortunately plausible in the twisted world of Kim Jong Un’s North Korea.”Mr Hyon, a little-known general, was promoted to the rank of vice-marshal of the North Korean army in 2012.

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.

If confirmed, the execution marks another demonstration of Mr Kim’s ruthlessness in dealing with even the most senior officials suspected of disloyalty, following the execution of his uncle and one-time political mentor Jang Song Thaek in 2013.

It also points to possible power struggles within the top leadership, following Mr Kim’s decision to cancel a scheduled visit to Moscow last week in order to deal with “internal issues”.

In 2013, Mr Kim purged and executed Jang, 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 Mr Kim took power.

Late last month, the NIS reported that Kim had ordered the execution of 15 senior officials so far this year, including two vice-ministers, for questioning his authority.

North Korea is one of the most insular countries in the world and its ruling power structure is highly opaque. The current leader is the third generation of the Kim family that has ruled with near-absolute power since the country was established in 1948.But the hierarchy around them has long been subject to infighting and factionalism which makes it impossible for outsiders to ascertain who makes decisions, and why.Mr Kim, who is in his early thirties, has changed his armed forces chief four times since coming to power. His father Kim Jong Il, who ruled over the isolated nuclear-capable country for almost two decades, replaced his chief just three times.