Pak Myong Ho, a minister at North Korea's embassy in Beijing, said the February 13 murder of Kim Jong Nam in Malaysia was a "despicable and extremely dangerous" plot by the US and South Korea aimed at smearing North Korea's image and subverting its regime.
Pak said "indiscriminate claims of behind-the-scenes manipulation" would fail, referring to allegations by South Korea's spy agency that North Korea masterminded the assassination.
Malaysian media say police confirmed Kim Jong Nam's identity using DNA from his son which was obtained overseas and brought to Malaysia.
The incident has led to a sharp deterioration of ties between Malaysia and North Korea, with each expelling the other's ambassador.
North Korea has blocked Malaysians from leaving the country until a "fair settlement" of the case is reached.