The estranged half-brother of North Korean leader Kim Jong-un has been killed in Malaysia, South Korean media reported, with one TV station saying he was attacked at the country's main airport with poisoned needles.

Officials in South Korea and Malaysia on Tuesday could not confirm the death of Kim Jong-nam. Malaysian police said a North Korean had been taken sick at Kuala Lumpur International Airport and since died.

A senior security source told Al Jazeera that Malaysian police "strongly" believe the deceased individual was Kim Jong-nam.

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In a statement, Malaysian police said the 46-year-old dead man was travelling on a passport under the name Kim Chol.

"Kim Jong-nam has been known to travel using a fake name," Al Jazeera's Florence Looi, reporting from the airport in Kuala Lumpur, said.

She added that the body of the deceased man had been taken to a hospital where an autopsy was being conducted.

Earlier on Tuesday, the Yonhap news agency said Kim Jong-nam was killed on Monday morning in Malaysia. It cited a South Korean government source but gave no more details.

TV Chosun, a cable television network, said separately that Kim Jong-nam was poisoned at Kuala Lumpur airport by two women believed to be North Korean operatives, who were at large, citing multiple South Korean government sources.

Kim Jong-nam and Kim Jong-un are both sons of former leader Kim Jong-il, who died in late 2011, but they had different mothers.

In 2001, Kim Jong-nam was caught at an airport in Japan travelling on a fake passport, saying he had wanted to visit Tokyo Disneyland.

He was known to spend a significant amount of his time outside North Korea, travelling to Hong Kong, Macau and mainland China.

He said several times over the years that he had no interest in leading his country.

"Personally, I am against third-generation succession," he told Japan's Asahi TV in 2010, before his younger brother had succeeded their father.

"I hope my younger brother will do his best for the sake of North Koreans' prosperous lives."

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Malaysia is one of a dwindling number of countries that has close relations with North Korea, which is under tightening global sanctions over its nuclear tests and ballistic missile launches, the latest of which took place on Sunday.

Malaysians and North Koreans can visit each other's country without visas.