South Korea has confirmed the killing of the brother of North Korea's leader Kim Jong-un, saying it could be a sign of the brutality of Pyongyang.

Kim Jong-nam was killed in an apparent poison attack in the Malaysian capital, Kuala Lumpur, on Monday.

No motive has been confirmed and the attackers have not been identified.

South Korea's acting president Hwang Kyo-ahn said if North Korea was found to be responsible, it would show its "brutality and inhumane nature".

If confirmed, it would be the most high-profile death at the hands of the North Korean leadership since Kim Jong-un's uncle, Chang Song-thaek, was executed in 2013.

Mr Kim appears to have been attacked with a chemical while preparing to board a flight home to Macau from in Kuala Lumpur's airport on Monday.

His death was made public only on Tuesday. On Wednesday morning, his body was released from hospital. A post-mortem examination was expected to be conducted.

A Malaysian police official, Fadzil Ahmat, told Reuters that so far there were no suspects, "but we have started investigations and are looking at a few possibilities to get leads".

Police are studying security camera footage from the airport. Images circulating in the media have focused on two women seen alongside Mr Kim, who were later seen leaving the scene in a taxi.

Unnamed US government sources have said they believe he was poisoned by North Korean agents, but there has been no official comment from the White House.

What happened?

Kim Jong-nam was attacked at about 09:00 (01:00 GMT) on Monday while waiting at the budget terminal of Kuala Lumpur International Airport for a 10:00 flight to Macau, Malaysia's Star newspaper reports, quoting police.

Exactly how the attack unfolded is still unclear. Officials and witnesses have variously said he was splashed with a chemical or had a cloth placed over his face.

Earlier reports spoke of a "spray" being used or a needle.

He died on the way to hospital.

Why the delay in identifying him?

South Korean media named the victim early on Tuesday but the Malaysian authorities initially reported only the sudden death of an unnamed North Korean national who had fallen ill at the airport.

Police then released a statement which quoted the victim's travel document identifying him as "Kim Chol", born on 10 June 1970. Kim Jong-nam is believed to have been born on 10 May 1971.

It was not the first time Mr Kim had travelled under an assumed identity: he was caught trying to enter Japan using a false passport in 2001. He told officials he had been planning to visit Tokyo Disneyland.

Why was he flying to China?

Bypassed in favour of his youngest half-brother for succession when their father died in 2011, Kim Jong-nam kept a low profile, spending most of his time overseas in Macau, mainland China and Singapore.

The Tokyo Disneyland incident is thought to have spoilt his chances of succeeding Kim Jong-il, who died in 2011.

He later spoke out against his family's dynastic control of North Korea and in a 2012 book, was quoted as saying he believed his younger half-brother lacked leadership qualities.

But he had said he was not interested in assuming the leadership himself.

Was this an assassination?

Mr Kim was reportedly targeted for assassination in the past.

A North Korean spy jailed by South Korea in 2012 was reported to have admitted trying to organise a hit-and-run accident targeting him.

The secretive state has a long history of sending agents overseas to carry out assassinations, attacks and kidnappings