Pyongyang is calling for the immediate release of suspects
North Korea has said Malaysia is to blame for the death of Kim Jong-Nam at an airport in Kuala Lumpur.
Pyongyang has also accused the Malaysian government of having an "unfriendly attitude" following the murder of Kim Jong-Un's estranged half-brother last week.
According to KCNA, the country's state news agency, Mr Kim "suddenly fell into a state of shock" and died after suffering what it called "a heart stroke" - and warned Malaysia's refusal to hand over his body showed a disregard for international law.
North Korean officials have challenged claims that the 45-year-old was poisoned, and said Malaysian police had "recklessly" made it an established fact.
Investigators believe two female suspects, who are currently in Malaysian custody, had been trained to coat their hands with toxic chemicals and then wipe them on Mr Kim's face.
But that account has been ridiculed by the KCNA, which asked how it would be possible for the female suspects to be alive if their hands had been covered with poison.
Pyongyang is calling for the immediate release of the pair, describing them as "innocent women".
US and South Korean officials believe Mr Kim was killed by agents from the secretive state - and investigators in Malaysia have identified a total of eight North Koreans suspects.
Security has been stepped up at the mortuary where Mr Kim's body is being held after an attempted break-in, as further tests are performed to determine how he died.
According to KCNA, the Korean Jurists Committee has expressed outrage at Malaysia's decision to perform two post-mortem examinations - describing it as "a wanton human rights abuse and an act contrary to human ethics and morality".
North Korea has proposed a joint investigation with Malaysia, and says it stands ready to send a delegation of jurists to "conclude the investigation into the incident in a fair way".
The country says it wants to meet suspects, hear their statements, asked who ordered them, and survey footage from the place where Mr Kim fell ill.