The United States government "strongly believes" that North Korean agents murdered Kim Jong-un's brother in Malaysia's Kuala Lumpur International Airport on Monday (13 February).
Kim Jong-nam had previously spoken out about his family's dynasty and fell from the family's good books in 2001 after attempting to visit Tokyo's Disneyland with a forged passport.
The 45-year-old is believed to have been assassinated in a "poisoned needles" attack by two women, who reportedly splashed a liquid in his face.
Two officials from the US government told Reuters reporters the dictatorship is thought to be behind the suspected murder. However, they offered no specific evidence to support the claim.
The White House has not responded to requests for comment and issued no statements on Jong-nam's death.
South Korea did not confirm reports that North Korea was responsible, but said the death was murder.
If confirmed as an assassination, it would be the latest in a string of killings over the decades at home and abroad to silence those perceived by North Korea's leaders as threats to their authority.
Malaysian police official Fadzil Ahmat said the cause of Jong-nam's death was not yet known, and that a post-mortem would be carried out.
"So far there are no suspects but we have started investigations and are looking at a few possibilities to get leads," Fadzil told Reuters.
Earler in the day, he described the final moments of Jong-nam's life before he was pronounced dead in Putrajaya Hospital.
"He told the receptionist at the departure hall that someone had grabbed him from behind and splashed a liquid in his face," he said.
"He asked for help from the receptionist and was immediately sent to the airport's clinic. At this point, he was experiencing a headache and on the verge of passing out."
Jong-nam was believed to be close to his uncle, Jang Song Thaek, who was North Korea's second most powerful man before being executed. reportedly on Kim Jong-un's orders, in 2013.
His cousin, Lee Han-young, who defected to South Korea through Switzerland in 1982, was shot and killed by North Korean agents in Seoul in 1997, according to South Korea.