Malaysian police have revealed they are seeking four more suspects over the death of the half brother of North Korea's leader.

Detectives say all four are North Korean citizens, and left Malaysia the same day as Kim Jong-Nam was attacked at Kuala Lumpur airport.

They also wish to speak to a further three people who may have information.

North Korean dictator Kim Jong-Un is suspected of ordering the killing.

His half brother was living in exile, and had been critical of the regime.

Four people are already in custody over his death.