Malaysian police on Wednesday named a North Korean diplomat along with a state airline official who are wanted for questioning over the murder of Kim Jong Nam, the estranged half-brother of North Korea's leader.

Kim Jong Nam, 46, was killed at Kuala Lumpur International Airport on Feb. 13, while preparing to board a flight to Macau, where he lived in exile with his family under the protection of Beijing.

South Korean and U.S. officials believe the killing of the elder half-brother of North Korean leader Kim Jong Un was an assassination carried out by agents of the North.

Kim Jong Nam had spoken out publicly against his family's dynastic control of the isolated, nuclear-armed state.

Giving an update on an investigation that has already angered North Korea, Malaysia's police chief Khalid Abu Bakar said the diplomat wanted for questioning was 44-year-old Hyon Kwang Song, a second secretary at the embassy.

Police also want to interview Kim Uk Il, 37, an employee of the North Korean state-owned airline Air Koryo.

Khalid said both were in Malaysia but could not confirm they were in the embassy.

"They've been called in for assistance. We hope the embassy will cooperate with us and allow us to interview them quickly or else we will compel them to come to us," Khalid told reporters.

"We can't confirm that they are hiding in the embassy," he told Reuters.

So far, police have identified a total of eight North Koreans suspected of being linked to killing.

One, Ri Jong Chol, has been in custody since last week, and another, Ri Ji U, remains at large. Khalid said police "strongly believed" four others were back in the North Korean capital of Pyongyang, having fled Malaysia on the day of the attack.

Police have not stated Ri Jong Chol's role in the killing. He lived in Malaysia for three years without working at the company registered on his employment permit or receiving a salary.

Police are also holding two women - one Vietnamese, one Indonesian - who are suspected of carrying out the fatal assault on Kim Jong Nam using a fast-acting poison.

REHEARSED ATTACK

Police chief Khalid said both women wiped a liquid, containing an as yet unidentified toxic substance, on Kim Jong Nam's face.

"Yes, the two female suspects knew that the substance they had was toxic. We don't know what kind of chemical was used," he said, dismissing speculation that the women had thought they were part of a prank.

"They used their bare hands," he said, adding that they were instructed to wash their hands afterwards.

The women had rehearsed the attack at two shopping malls in central Kuala Lumpur before assaulting Kim Jong Nam, he said.

An Indonesian foreign ministry official Lalu Muhammad Iqbal said it was premature to draw conclusions about its citizen's involvement.

"The fact that investigators have asked for an extension to the remand shows that the evidence so far is not enough to bring charges or prosecute," he said in a statement.

DIPLOMATIC SPAT

North Korea's embassy issued a statement on Wednesday calling for the immediate release of its citizen, Ri Jong Chol, and the two women, saying they were innocent. The embassy statement did not address the police request to interview one of its diplomats.

Security was stepped up at the morgue where Kim Jong Nam's body is being held after an attempted break-in earlier this week, Khalid said.

Malaysia has denied North Korea's request for the body to be handed over to its embassy directly, saying it would be released to the next of kin, though none has come forward.

The investigation has strained Malaysia's hitherto friendly relations with North Korea.

Earlier this week Malaysia recalled its ambassador from Pyongyang, and Prime Minister Najib Razak rebuked the North Korea ambassador in Kuala Lumpur for making "diplomatically rude" comments.