Malaysian police said Sunday they were seeking four more North Korean suspects in the assassination of Kim Jong-Un's half-brother at Kuala Lumpur's main airport, but the four had already left the country.

The suspects were all male and aged between 33 and 57, Deputy Inspector-General of Police Tan Sri Noor Rashid Ibrahim told a press conference. 

In addition to the four, three North Koreans were being sought to assist with enquiries.

Police on Saturday arrested a North Korean man over the killing last Monday of Kim Jong-Nam after detaining a woman carrying a Vietnamese passport, as well as an Indonesian woman and a Malaysian man.