North Korea has tried to shift the blame for the deadly attack in Malaysia on the estranged half-brother of its leader Kim Jong Un to the United States and South Korea.

North Korea's deputy UN ambassador, Kim In Ryong, told a news conference that "from A to Z, this case is the product of reckless moves of the United States and South Korean authorities," who he said are trying to tarnish the North's image and bringing down its social system.

Malaysian authorities say Kim Jong Nam died after two women smeared his face with the banned VX nerve agent at Kuala Lumpur's airport on February 13, but North Korea which is widely suspected to be behind the attack rejects the findings.

Ambassador Kim said the cause of Kim Jong Nam's death "has not yet been clearly identified, but the United States and the South Korean authorities are groundlessly blaming the DPRK," using the initials of the North's official name, the Democratic People's Republic of Korea.

Malaysian authorities have identified the victim as Kim Jong Nam, though he was using a North Korean passport under the name Kim Chol. The ambassador, like other North Korean officials, referred to him only as Kim Chol and did not say he was Kim Jong Un's half brother.

He asked why the person who applied the VX agent, which is fatal if a tiny amount is inhaled, is still alive while the man it was applied to died.

The ambassador asserted that the US is one of the few countries that can manufacture VX and that it has stockpiled chemical weapons in South Korea, which could have provided the chemical agent for the attack on Kim Jong Nam.

"It is a final aim sought by the United States to store up the international repugnancy towards the DPRK," he said of the attack, with the intention of provoking a "nuclear war against DPRK at any cost." 

"So the US and South Korea were starting the political chicanery to bring down the social system in DPRK," the ambassador said.

He said the DPRK will respond by continuing to bolster its defenses "and the capability for the pre-emptive strike with a nuclear force." 

The North Korean envoy held a press conference at UN headquarters in New York after the DPRK boycotted a meeting of the UN Human Rights Council in Geneva, which was addressed by its special investigator on human rights in the reclusive northeast Asian nation.

Tomas Ojea Quintana told the council that tensions caused by North Korea's ballistic missile and nuclear tests are jeopardizing efforts to improve human rights in the secretive country.