Kim Jong-nam, the half-brother of North Korean leader Kim Jong-un, was assassinated in Kuala Lumpur airport, Korean-language media reported late on Tuesday.
Kim Jong-nam, 45, was reportedly killed by poison needle by two women who fled the scene by taxi, the reports said.
He was once considered to be an heir to late North Korean leader Kim Jong-il, but his fortunes turned after being arrested at Tokyo airport for using a fake passport. He was apparently en route to Disneyland.
A source close to the Malaysian prime minister’s office said that police were still waiting for an autopsy.
South Koreans officials have yet to comment.
Mr Kim was a well-known face at the gambling tables of Macao, where he lived as an exile for many years.
He speaks good English and chats affably with reporters. Like his brothers, Mr Kim also grew up in a cloistered world, but with privileged access to to foreign films and luxury goods.
His son, Kim Han-sol, attended a university in Paris for about a year from September 2013.
North Korea has a long history of extraterritorial murders and defectors from the reclusive state are often warned about roving agents.
In 1983, North Korean agents killed 21 people in a failed bombing attempt on then South Korean leader Chun Doo-hwan while the leader was on a state visit to Myanmar.
Four years later, 115 were killed after two North Korean agents planted a bomb on Korean Air Flight 858 between Baghdad and Seoul.
The assassins were apprehended while trying to escape from Bahrain airport, with both immediately attempting suicide by ingesting cyanide.
One died immediately, while the other was extradited to Seoul where she was sentenced to death but later pardoned.