Investigators have put five North Koreans in the frame for last week's brazen killing of Kim Jong-Nam at Kuala Lumpur International Airport and have said they are seeking three more for questioning.
They include the embassy's second secretary, Hyon Kwang Song, as well as a North Korean airline employee called Kim Uk Il, Khalid Abu Bakar told reporters.
"We have written to the ambassador to allow us to interview both of them. We hope that the Korean embassy will cooperate with us and allow us to interview them quickly. If not, we will compel them to come to us," he said.
Jong-Nam died on February 13 after being attacked as he waited for a plane to Macau.
Leaked CCTV footage from the airport shows the chubby 45-year-old being approached by two women, one of whom grabs him from behind and appears to shove a cloth in his face.
Moments later Jong Nam is seen seeking help from airport staff, who direct him to a clinic, where he apparently slumped in a chair.
Malaysian police say he suffered a seizure and died before he reached hospital, seemingly from the effects of a toxin.
Seoul has said from the start that Pyongyang was behind the murder, citing a "standing order" from Jong-Un to kill his elder sibling, and a failed assassination bid in 2012.
Trained killers
Asked whether the five North Korean suspects had masterminded the attack, Khalid said he believed they were "heavily involved" in the murder.
Four of the men fled the country on the day of the killing and returned to Pyongyang, he said, while one remains in custody in Malaysia.
The police chief dismissed claims the two women had believed the attack was a made-for-TV prank.
"Of course they knew" it was a poison attack, Khalid said. "I think you have seen the video, right? The lady was moving away with her hands towards the bathroom. She was very aware that it was toxic and that she needed to wash her hands."
Khalid said Vietnamese suspect Doan Thi Huong, 28, and Indonesian Siti Aishah, 25, had been trained to swab the man's face, practising in Kuala Lumpur before the assault at the airport.
Aishah wiped a toxic substance in his face first, followed by Huong, the national police chief said.
The Indonesian's Malaysian boyfriend, who was arrested in the first days of the probe, has been released, he added.
But Pierre Champy, a chemist at the French National Centre for Scientific Research, cast doubt on the theory that the toxin acted by passing through the skin.
"I don't know of a toxin powerful enough to act by penetrating the skin that would kill so quickly. But it could have been a spray, entering via his lungs or mouth, or a small injection device," he said.
Pyongyang and Kuala Lumpur have locked horns over the investigation, with North Korea's envoy on Wednesday calling for Malaysia to release the two women and the North Korean citizen from police custody.
"They should immediately release the innocent females from Vietnam and Indonesia as well as a DPRK citizen," ambassador Kang Chol said in a statement which repeated allegations that South Korea had influenced the probe.
The women must have been framed as they would have died if they had carried the poison in their hands, the ambassador claimed. He did not address news that police were seeking to question an embassy official.
The diplomatic row erupted after North Korea objected to an autopsy of Jong-Nam's body and insisted that his remains be returned to Pyongyang.
Malaysia rejected the request, saying the remains must stay in the morgue until a family member identifies them and submits a DNA sample.
No next-of-kin have come forward, police chief Khalid said, adding rumours that Jong-Nam's son Kim Han-Sol was in Malaysia were not true.
First born Jong-Nam was once thought to be the natural successor to his father, the then-North Korean leader Kim Jong-Il.
But after Jong-Il's death in 2011 the succession went instead to Kim Jong-Un, a child of a later marriage.
Some analysts have said Jong-Nam was a marked man since he criticised the regime in 2011 to a Japanese journalist, while others said the killing could have been ordered over reports he was readying to defect.
