Malaysia has requested Interpol to put an alert out to apprehend four North Korean suspects in the murder of Kim Jong Nam.
The estranged half brother of North Korean leader Kim Jong Un was killed in Kuala Lumpur's main airport last week, in what South Korean and US officials say was an assassination carried out by North Korean agents.
Malaysia's police chief Khalid Abu Bakar said on Thursday that two women - one Vietnamese, one Indonesian - arrested last week had been paid for carrying out the fatal assault on Kim using a fast-acting poison, but declined to say if they were working for a spy agency.
Police are also holding one North Korean man, but are seeking another seven in connection with the murder.
Three of them - a diplomat, a state airline official, and another man - are believed to still be in Malaysia.
The other four are believed to have fled Malaysia on February 13, the day of the killing.
Khalid told reporters that a request had been made to Interpol to put out an alert to apprehend the four suspects, who they believe have already made their way back to North Korea.
Khalid also said the police have sent an official request to the North Korean embassy requesting to interview the embassy's second secretary and the airline official, having released their names on Wednesday.
"If you have nothing to hide, you should not be afraid to co-operate, you should co-operate," Khalid told reporters.
Khalid said an arrest warrant will not be issued for the second secretary, as he has diplomatic immunity, but that "the process of the law will take place" if the airline official does not come forward.
Police have still to receive DNA samples from Kim Jong Nam's next of kin, Khalid said. He also denied that Malaysian police officers had been sent to Macau, the Chinese territory where Kim and his family had been living under Beijing's protection.
North Korea's ambassador has said the Malaysian investigation cannot be trusted, and the embassy issued a statement on Wednesday saying that the three suspects that have been detained should be released.
