North Korean female agents using poisoned needles have assassinated the half-brother of the North's leader Kim Jong-Un in Malaysia, South Korean media reported Tuesday.

Officials in Seoul and Kuala Lumpur could not confirm the death of Kim Jong-Nam, once seen as heir apparent in the North.

Malaysian police said in a statement late Tuesday that a North Korean man, identified as Kim Chol, sought medical assistance at Kuala Lumpur International Airport and died on the way to hospital.

South Korean media reports meanwhile said Jong-Nam had travelled using a fake passport under the name of Kim Chol.

If confirmed, it would be the highest-profile death under the Jong-Un regime since the execution of the leader's uncle Jang Song-Thaek in December 2013.

Jong-Un has been trying to strengthen his grip on power in the face of growing international pressure over his country's nuclear and missile programmes. He has reportedly staged a series of executions.

The latest launch of a new intermediate-range missile on Sunday brought UN Security Council condemnation and vows of a strong response from US President Donald Trump.

South Korea's national news agency Yonhap quoted a source as saying agents of the North's spy agency, the Reconnaissance General Bureau, carried out the assassination on Monday by taking advantage of a security loophole between Jong-Nam's bodyguards and Malaysian police at the airport.

The 45-year-old was killed by two unidentified female agents using poisoned needles at the airport, according to South Korean broadcaster TV Chosun.

It said the women hailed a cab and fled immediately afterwards.

Jong-Nam, the eldest son of former leader Kim Jong-Il, was once seen as heir apparent but fell out of favour following an embarrassing botched attempt in 2001 to enter Japan on a forged passport and visit Disneyland.

He has since lived in virtual exile, mainly in the Chinese territory of Macau.

Jong-Nam's half-brother Jong-Un took over as leader when their father died in December 2011.

Jong-Nam, known as an advocate of reform in the North, once told a Japanese newspaper that he opposed his country's dynastic power transfers.

He was reportedly close to his uncle Song-Thaek, once the North's unofficial number two and political mentor of the current leader.

Targeted in the past

Cheong Seong-Jang, senior researcher at Seoul's Sejong Institute think-tank, said Jong-Nam had been living in near-exile so it was unlikely that Jong-Un saw him as a potential competitor for power.

“But if Jong-Nam committed an act to damage Jong-Un's authority, I think it's possible that the Reconnaissance General Bureau may have directly conducted the assassination under the orders of Jong-Un since it has been in charge of closely watching Jong-Nam.”

Jong-Nam has been targeted in the past.

In October 2012 South Korean prosecutors said a North Korean detained as a spy had admitted involvement in a plot to stage a hit-and-run car accident in China in 2010 targeting him.

In 2014, Jong-Nam was reported to be in Indonesia - sighted at an Italian restaurant in Jakarta - and was said to be shuttling back and forth between Singapore, Indonesia, Malaysia and France.

In 2012, a Moscow newspaper reported that Jong-Nam was having financial problems after being cut off by the Stalinist state for doubting its succession policy.

Last year South Korea warned of possible North Korean assassination attempts in its territory.

It noted previous attempts to assassinate Hwang Jang-Yop, the North's chief ideologue and former tutor to Kim Jong-Il, who defected to the South in 1997 and died of natural causes in 2010.

Jong-Nam was born from his father's extra-marital relationship with Sung Hae-rim, a South Korean-born actress who died in Moscow.