(ATTN: EXPANDS dateline; UPDATES with details throughout)
SEOUL/KUALA LUMPUR, Feb. 15 (Yonhap) -- North Korean leader Kim Jong-un's half brother was murdered with poison in Malaysia, multiple sources including South Korea's spy agency said Wednesday, with the local police tracking down two women and four men who may be implicated in the crime.
Kim Jong-nam, 46, was at the airport to take a flight to Macao when he asked the staff for help after interacting with two "Asian" women. Kim died on the way to a nearby hospital.
The Malaysian authorities presume Kim was poisoned, although the details must be revealed through an autopsy.
Local law enforcement authorities have been narrowing down suspects based on security camera footage, with one of the six -- an unidentified woman -- getting arrested at the Low Cost Carrier Terminal at Kuala Lumpur International Airport.
The arrested woman, born in 1988, held a Vietnamese passport with the name "Doan Thi Huong."
"Suspect was positively identified from the CCTV footage at the airport and was alone at the time of arrest," the Malaysian police said in a release. "Investigation continues and any further actions against suspect/suspects will be taken in accordance with the law."
South Korea's National Intelligence Service (NIS) Director Lee Byong-ho told lawmakers earlier in the day that for the past five years Pyongyang has been attempting to assassinate Kim Jong-nam, who was under the protection of the Chinese government.
During a meeting with the National Assembly's Intelligence Committee, Lee confirmed that Kim was killed with poison at the airport, although it is still unclear whether a needle or chemical spray was used. The agency conceded it was notified of the incident about four hours after it occurred.
The NIS chief said there was also an assassination attempt in 2012, and that the North's latest action is presumed to have been based on Kim Jong-un's "delusional disorder," rather than on any calculation that his half brother is a threat to the regime.
Kim had also sent a letter to North Korean leader Kim Jong-un in 2012, pleading with his brother to spare his life and the lives of his family, the NIS said.
Kim Jong-nam's wife is currently staying in Beijing with a son, while his second wife is living in Macao with a son and a daughter. All of them are currently under the protection of Chinese authorities.
The son in Macao is Kim Han-sol, who came into the spotlight in 2012 after being interviewed by a Finnish television station. He said he hopes for the unification of the two divided Koreas and wants to improve the livelihoods of ordinary people living in the impoverished country now controlled by his young uncle.
The agency said Kim has never asked South Korea for asylum, nor was there any effort within North Korea to make Kim Jong-nam the leader.
Experts said that Kim might have been killed as the North Korean leader's move to strengthen his reign of terror by eliminating any potential rivals to his iron-fisted rule.
Kim Jong-nam -- the eldest son of late former leader Kim Jong-il -- had been living in foreign countries for years after apparently falling out of favor with his father for attempting to enter Japan with a fake passport in 2001.
He was critical of the power succession to his brother Kim Jong-un. In 2010, Kim Jong-nam told Japan's TV Asahi that he is "against third-generation succession," although he said he hopes Kim Jong-un will do his best to improve the lives of North Koreans and that he stands ready to help from abroad.
It marks the highest-profile death under the Kim Jong-un regime since the execution of Jang Song-thaek in December 2013, the once-powerful uncle of the incumbent leader.
Since inheriting power from his father Kim Jong-il in late 2011, the North's young leader has propped up his control by executing more than 100 military, party and government officials, according to Seoul's spy agency.
Experts said the incident will also have an adverse impact on the relationship between North Korea and Malaysia. The two countries clinched diplomatic ties in 1973 and maintain a sound relationship by mutually providing visa-free entry agreements.
If Kim Jong-un was behind the alleged assassination, experts say the action could be considered a grave crime that breaches the sovereignty of Malaysia.
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