LATEST: Woman arrested in Malaysia over death of N Korean leader's half-brother

Kim Jong Nam died on Monday after suddenly falling ill at the airport.

According to a Malaysian government official, Kim told medical workers before he died that he had been attacked with a chemical spray.

Earlier:

Police in Malaysia were checking airport surveillance video for clues about the astonishing assassination of North Korea leader Kim Jong Un's half-brother at a busy airport.

News of the death of Kim Jong Nam rippled across Asia today as police looked at CCTV footage for clues about the two female assailants and rival South Korea said Pyongyang had been trying to kill him for for five years.

The 46-year-old was targeted on Monday in a shopping concourse at Kuala Lumpur International Airport. He had not yet gone through security.

Kim, who died on the way to a hospital, told medical workers before he died that he had been attacked with a chemical spray, a senior government official said.

South Korea's spy service said today that North Korea had been trying for five years to kill him, citing Kim Jong Un's "paranoia" about his estranged half-brother.

Kim Jong Nam had been tipped by some outsiders as a possible successor to his dictator father, although others thought that was unlikely because he lived outside the country, including recently in Macau, Singapore and Malaysia.

He reportedly fell further out of favour when he was caught trying to enter Japan on a false passport in 2001, saying he wanted to visit Tokyo Disneyland.

Multiple South Korean media reports said he was killed at the airport by two women believed to be North Korean agents. They fled in a taxi and were being sought by Malaysian police.

Malaysian police confirmed the death of a 46-year-old North Korean man whom it identified from his travel document as Kim Chol, born in Pyongyang on June 10, 1970.

"Investigation is in progress and a post-mortem examination request has been made to ascertain the cause of death," the police said.

Ken Gause, of the CNA think tank in Washington who has studied North Korea's leadership for 30 years, said Kim Chol was a name that Kim Jong Nam has travelled under.

He is believed to have been born on May 10, 1971, although birthdays are always unclear for senior North Koreans, Mr Gause said.

The killing came as North Korea celebrated its latest missile launch, which foreign experts were analysing for evidence of advancement in the country's missile capabilities.

Since taking power in late 2011, Kim Jong Un has executed or purged a series of high-level government officials in what the South Korean government has described as a "reign of terror".

The most spectacular was the 2013 execution by anti-aircraft fire of his uncle, Jang Song Thaek, once considered the country's second-most-powerful man, for what the North alleged was treason.

North Korean assassins reportedly tried to shoot Kim Jong Nam in Macau in 2011, though the details of the attempted killing are murky.

South Korea also reportedly jailed a North Korean spy in 2012 who admitted to trying to organise a hit-and-run accident targeting Kim Jong Nam in China in 2010.

Despite the attempts on his life, Kim Jong Nam had reportedly travelled to North Korea since then, so it was assumed he was no longer under threat.

While the most likely explanation for the killing was that Kim Jong Un was removing a potential challenger to North Korean leadership within his own family, he could also be sending a warning to his officials.

It follows the defection last year of a senior diplomat from the North Korean Embassy in London who has spoken of his despair at Kim's purges.