Yonhap, citing a South Korean government source, said Kim Jong-nam was killed on Monday morning in Malaysia. It gave no more details.
TV Chosun, a cable television network, said separately that Kim 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.
The reports could not be independently verified.
Malaysian police told the Reuters news agency an unidentified North Korean man died en route to hospital from a Kuala Lumpur airport.
The police said the man’s identity had not been verified.
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.