KUALA LUMPUR (THE STAR/ASIA NEWS NETWORK) - Four North Korean suspects being hunted by Malaysian police for the murder of Mr Kim Jong Nam, half-brother of the North Korean leader, are believed to be back in Pyongyang after leaving the country for Jakarta immediately after the attack.

The four - Rhi Ji Hyon, 33; Hong Song Hac, 34; O Jong Gil, 55; and Ri Jae Nam, 57, left for Jakarta after the attack on Feb 13. From there, they flew to Dubai and Vladivostok, Russia, before reaching Pyongyang, said sources.

"They may have taken the long route to shake off the authorities," the sources said.

Deputy Inspector-General of Police Tan Sri Noor Rashid Ibrahim said Malaysian police are cooperating with Interpol and other relevant bodies overseas to track them.

The police's first priority is to collect all evidence on the suspects' involvement in the case.

"Next plan is to get them. We will use all resources to pursue them," he told a press conference on Sunday, the first by the police since the killing of Mr Kim Jong Nam.

On the possibility that the murder was politically motivated, the deputy police chief said the police were not interested in any political angle.

"What we are interested in is why they committed such a crime in our country.

"Any political angle can be put aside as it is not our job to worry about political matters,'' he said. "We want to get at the truth and bring the perpetrators to justice."

He said police were also looking for North Korean citizen Ri Ji U, 30, also known as James, along with two others to help in investigations.

On the post-mortem, he said it was conducted on Feb 15 at Hospital Kuala Lumpur.

"The cause of death is still unknown. We are waiting for the toxicology and pathological test results. I think in a few days, we will get the toxicology result.

"The case will be referred to the deputy public prosecutor for further instructions and investigation," he said.

Priority is given to close family members or next of kin to claim the body and they have been given two weeks to do so, he added.

"It is very important for close family members of the deceased to come forward to assist us in the process of identification, which is based on our legal procedures and Malaysian law.

"However... we have not met the next of kin. We are trying very hard to get the next of kin to assist us," he said.

In the event that the family does not show up, he said the police will look at further options.