Kim Jong-Nam's modest life in Macau was a far cry from the opulence and power enjoyed by his half-brother, the supreme leader of North Korea, but he was still seen by Pyongyang as a dangerous pretender to the ruling family throne.

Friends in the Chinese gambling enclave spoke this week of a man who wined and dined in relative freedom, despite what Seoul's spy chiefs say was a "standing order" for his execution, issued by Kim Jong-Un.

His younger brother's order was fulfilled this week, Seoul says, when Jong-Nam was murdered at an airport in Malaysia, the victim of poison-wielding female assassins sent by North Korea.

People who knew the elder Kim in Macau painted a picture of a man who often lived with little security and was not overly cautious.

"I think it was simply not in his character," one friend told Hong Kong's South China Morning Post, noting that Kim would stay in Macau and overseas without bodyguards.

"He had a relaxing life here. Obviously he felt he was protected by China," the friend said.

"Macau suited his personality. He enjoyed life and the good things about it. Macau offered him security and also entertainment."

"He was very cheerful and mingled easily," the friend told the Post, adding Kim was involved in charity work for South Koreans.

A slightly drab apartment complex where Kim was believed to have lived was largely deserted when AFP visited this week.

Cantonese-speaking residents denied knowing a man who was educated in Europe and divided his time between Paris, China and the former Portuguese colony, and who moved freely around Asia.

His body on Friday lay in a Kuala Lumpur morgue, with Malaysian police saying they would not hand it over until a family member offered a DNA sample to positively identify it.

- Three reasons -

Kim, the first son of late North Korean leader Kim Jong-Il, was at one time set to take the reins of power in the isolated state; groomed by his father for a third generation succession.

Exactly what changed his father's mind is unclear, but a botched 2001 attempt to get into Japan on a fake passport -- apparently to visit Disneyland -- is commonly cited as the fatal blot on his copybook.

From exile he was a periodic commentator on North Korean affairs, quoted by Japanese journalist Yoji Gomi, who published a book about him in 2012, as claiming the regime would "collapse" without reform.

He had even dubbed the North's hereditary succession a "laughing stock", and told Gomi that Jong-Un would "not last" as leader.

In the deeply patriarchal North the first son is seen as the official heir of the family: founding father Kim Il-Sung passed the role to his first son Kim Jong-Il upon his death in 1994.

Kim Jong-Un's status as merely the son of Kim Jong-Il's third wife was seen as a taint on his credentials as leader, according to observers.

"The assassination, if confirmed done by the North, would be a sign of Kim Jong-Un's paranoid personality," Seoul lawmaker Kim Byung-Kee quoted the South's spy chief as saying in a closed-door briefing on Wednesday.

For Jun Byung-Kon, an analyst at the Korea Institute for National Unification, China could also have been a factor.

Beijing remains the impoverished North's economic lifeline and sole diplomatic ally, although ties have soured following a series of nuclear and missile tests staged after Kim took the helm following the 2011 death of his father.

"Even after Kim Jong-Un took power, there was this atmosphere in China that the open-minded Kim Jong-Nam was far better suited as leader," he said.

That gave Kim Jong-Un three reasons to want his older brother dead, said Hong Hyun-Ik of the Sejong Institute think tank in Seoul.

"Apart from his open criticism on the North, Jong-Nam is older, the legitimate first son...and supported by China," he said.

"They are enough reasons from Jong-Un's perspective to kill him."