Malaysian PM has said his country had "no reason to paint North Korea in a bad light"
North Korea has demanded to see the suspects detained over the apparent assassination of Kim Jong-Un's half-brother, saying the investigation by the Malaysian authorities cannot be trusted.
Kang Chol, North Korea's ambassador to Malaysia, said authorities had "pinned the suspicion on us" and asserted the probe into Kim Jong-Nam's death was politically motivated and "in collusion with South Korea".
He told reporters on Monday: "It has been seven days since the incident but there is no clear evidence on the cause of the death and at the moment we cannot trust the investigation by the Malaysian Police.
"It only increases the doubt that there is someone else's hand behind the investigation."
Najib Razak, Malaysia's Prime Minister, immediately rejected the allegations and said his country had "no reason to paint North Korea in a bad light" and insisted "we will be objective".
Kim Jong-Nam was targeted at Kuala Lumpur International Airport on 13 February. He was apparently travelling under the alias of Kim Chol and was waiting to board a flight to Macau at the time of the attack.
South Korea has accused Pyongyang of ordering the murder, saying two female assassins poisoned the 45-year-old then fled in a taxi
Pyongyang has demanded that Kim Jong-Nam's body be returned but Malaysia has refused the request, saying it must remain until identified through a DNA sample from a family member.
A relative has yet to come forward and a cause of death has still not been established.
On Saturday, a Malaysian newspaper published an image of him slumped in a chair immediately after the attack.
He died on his way to hospital.
CCTV has also since emerged allegedly showing the moment he was murdered.
Four people have been arrested so far in connection with his death.
Police are hunting four North Koreans who fled Malaysia as Kim Jong-Nam was being killed and another three are being sought to assist police with their enquiries.
The ambassador slammed the request for a DNA sample as "preposterous".
Referring to the victim as Kim Chol, he demanded a meeting with the suspects and a joint probe to "reveal the truth".
"Some people say the suspects are instructed by someone else. We would like to hear from them directly to ensure by whom they were instructed," he said.
He accused South Korea of "spreading false propaganda through mass media" and said the North would not "tolerate any criticism against it".
"Now there are so many rumours spread to the public to defame the image of the DPRK," he said.
"All the happenings clearly show that this incident is politicised by Malaysia in collusion with South Korea," he added.
Kim Jong-Nam was a known advocate of reform in North Korea and was vocal about his opposition to the nation's dynastic succession policy, but never defected or led a campaign against his younger sibling.
He had been living in the Chinese territory of Macau, under China's protection.
South Korean intelligence chiefs believe his killing was an assassination ordered by Kim Jong-Un some time ago because the North Korean leader perceived his half-brother to be a threat.