An arrest warrant has been issued for an airline employee accused over the death of Kim Jong-nam, the half-brother of North Korean leader Kim Jong-un.

National police chief Khalid Abu Bakar said on Friday that the warrant was issued for 37-year-old Kim Uk Il, who works for Air Koryo.

Police say he arrived in Malaysia about a fortnight before Kim Jong-nam was attacked with VX nerve agent in an airport in Kuala Lumpur.

The country is looking for seven North Korean suspects in total, four of whom are believed to have left the country.

One of the suspects thought to to still be in Malaysia is an official at the North Korean Embassy.

The only people currently in custody are two women - one Indonesian, one Vietnamese - accused of putting the nerve agent on his face.

They have not said why they want to question Kim Uk Il, but believe he is still in Malaysia.

Earlier on Friday, they released another North Korean, citing a lack of evidence.