(AFP) - The body of the assassinated half-brother of North Korea's leader is to undergo an autopsy on Wednesday, police said as they searched for those responsible for the Cold War-style killing at a Malaysian airport.

Two women are believed to have used some kind of poison to kill Kim Jong-Nam, with reports from Malaysia and South Korea saying he had been stabbed with poison-tipped needles or had chemicals sprayed in his face.

The assassination, which came as North Korea readied to celebrate the birthday this week of the two men's father, illustrates the "brutal and inhuman" nature of the Pyongyang regime led by Kim Jong-Un, Seoul said.

Police in Malaysia were examining CCTV footage from Kuala Lumpur International Airport to try to determine what happened during the attack on Monday morning.

"He told the receptionist at the departure hall that someone had grabbed his face from behind and splashed some liquid on him," Selangor state's criminal investigation chief Fadzil Ahmat was reported as saying by Malaysia's The Star newspaper.

"He asked for help and was immediately sent to the airport’s clinic. At this point, he was experiencing headache and was on the verge of passing out,” said Fadzil.

"At the clinic, the victim experienced a mild seizure. He was put into an ambulance and was being taken to the Putrajaya Hospital when he was pronounced dead," he said.

South Korean reports had earlier suggested the two female assassins had used poison-tipped needles during the killing, before fleeing in a taxi.

- Fall from grace -

Kim had at one time been set to assume the leadership of his isolated country, but fell out of favour after an embarrassing attempt to get into Japan on a fake passport in 2001.

He has since lived in exile, mostly in the gambling haven of Macau, but he has also been spotted in other Asian countries and there have been reports of his playboy lifestyle.

Kim, 45, is believed to have been in Malaysia on a passport bearing the name Kim Chol, a known alias, according to South Korean media.

But Seoul on Wednesday confirmed that the dead man was a member of the Kim dynasty.

"Our government is certain that the murdered man is Kim Jong-Nam," said Chung Joon-Hee, a spokesman for Seoul's unification ministry that handles inter-Korea affairs.

"If confirmed, the murder of Kim Jong-Nam would be an example that shows the brutality and inhumane nature of the North Korean regime," acting leader Hwang Kyo-Ahn told a meeting of top security officials earlier, according to his spokesman.

"We're taking this incident very seriously and we're keeping close tabs on the North", Hwang said.

In Pyongyang, celebrations had begun for Thursday's anniversary of the birth of Kim Jong-Il, Jong-Nam's father, with no mention of the killing.

Around 3,000 uniformed government officials and women in traditional dresses gathered for an ice skating gala featuring North Korean and foreign skaters. Banners proclaiming "peace", "independence" and "friendship" hung in the venue.

Kim's killing is thought to 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, and regular reports have emerged on purges and executions.

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

In a 2012 interview from his school in Bosnia, a 17-year-old Kim Han-Sol, Jong-Nam's son, said his father had been passed over for succession because he "was not really interested in politics".

"I don't really know why he became a dictator," Kim said of his uncle Kim Jong-Un. "It was between him and my grandfather."

Cheong Seong-Chang of the independent Sejong Institute in Seoul said it was unlikely Jong-Un saw his elder brother as a potential competitor for power, but that his assassination was "unthinkable without a direct order or approval from Kim Jong-Un himself".

His killing was likely motivated by a recent news report that Kim Jong-Nam had sought to defect to the EU, the US or South Korea as far back as in 2012, he said.

© Agence France-Presse