Malaysia has reached a deadlock in its probe into the apparent assassination last month of the estranged half brother of North Korean leader Kim Jong Un at Kuala Lumpur International Airport.

The killing of Kim Jong Nam, who had criticized North Korea's hereditary succession in an interview with a Japanese newspaper, was a crime planned by the reclusive country, South Korean intelligence has said.

Malaysia's investigative options are running out, as only two women — an Indonesian and a Vietnamese both in their 20s — have so far been charged with the murder of Kim Jong Nam, the eldest son of late North Korean leader Kim Jong Il.