Kim Jong-nam, the half-brother of North Korea's leader, was killed by a highly toxic nerve agent, says Malaysia.

Mr Kim died last week after two women accosted him briefly in a check-in hall at a Kuala Lumpur airport.

Malaysian toxicology reports indicate he was attacked using "VX nerve agent", which is classified as a weapon of mass destruction by the United Nations.

There is widespread suspicion that North Korea was responsible for the attack, which it fiercely denies.

It responded furiously to Malaysia's insistence on conducting a post-mortem examination and has accused Malaysia of having "sinister" purposes.

The well-travelled and multilingual oldest son of late North Korean leader Kim Jong-il, he was once considered a potential future leader. He has lived abroad for years and was bypassed in favour of his half-brother, Kim Jong-un.

How did he die?

A woman was seen in CCTV footage approaching Mr Kim and wiping something across his face. He sought medical help at the airport, saying someone had splashed or sprayed him with liquid.

He had a seizure and died on the way to hospital.

Who did it?

Malaysia says it was clearly an attack by North Korean agents. Four people are in custody, including one North Korean and the two women he interacted with at the airport. Seven North Koreans are being sought, including a diplomat.

Mr Kim died on the way to hospital shortly after the 13 February airport encounter. His body remains in a hospital mortuary, amid a diplomatic dispute over who should claim it.

Malaysia's police chief Khalid Abu Bakar said on Friday that the presence of the nerve agent was detected in swabs taken from Mr Kim's eyes and face by the Chemistry Department of Malaysia.

He said other exhibits were still under analysis and that police were investigating how the banned substance might have entered Malaysia.

"If the amount of the chemical brought in was small, it would be difficult for us to detect," Reuters quoted him as saying.

One of the two women suspected of carrying out the attack had also shown symptoms, he said, and had been vomiting.

Mr Khalid said the airport and areas the suspects are known to have gone to would now be cleaned.