North Korea on Thursday dismissed the Malaysian investigation into the mysterious death of the half brother of the North’s leader Kim Jong-un, accusing the Southeast Asian country of conspiring with South Korea to sabotage the regime.

In its first official reports since the death of Kim Jong-nam, the state-run KCNA news agency claimed Malaysia had initially told them that the victim died of a supposed “heart stroke,” but changed its position after “false reports” surfaced in South Korea that he had been poisoned to death in an apparent assassination.

South Korea, in response, pledged to seek tougher measures against North Korea -- such as a plan to demand the US put Pyongyang back on a list for state sponsors of terrorism -- and warned the regime would attempt military provocation as a distraction.

“What merits more serious attention is the fact that the unjust acts of the Malaysian side are timed to coincide with the anti-DPRK conspiratorial racket launched by the South Korean authorities,” the KCNA said, citing a spokesman at the reclusive regime’s jurists committee.

“The biggest responsibility rests with the government of Malaysia as a citizen of the DPRK died in its land,” the report added, referring to the victim only as “a citizen of the DPRK,” using North Korea’s official name, the Democratic People’s Republic of Korea and not mentioning the person’s name.

Seoul’s Vice Foreign Minister Lim Sung-nam on Thursday told lawmakers that the government would negotiate with Washington over a plan to add Pyongyang to the list as a terrorism state. Washington took the regime off the list in 2008 as a goodwill gesture on efforts being made for the North to resolve its nuclear issues.

In the wake of Pyongyang’s latest ballistic missile test last month, however, calls are emerging in the US Congress to add the regime to the terrorism list. Rep. Ted Poe introduced a bill calling for the measure in January and the legislation was referred to congressional subcommittees last week.

“We will negotiate with Washington and, if necessary, play our parts” to designate the North as a state sponsor of terrorism, Lim told the lawmakers, saying the murder of Kim would offer “impetus” to the effort.

During the same meeting with lawmakers, Unification Minister Hong Yong-pyo repeated the government’s claim that North Korea would plot terrorism attacks against South Korea to distract attention away from what Seoul viewed as assassination of a member of Pyongyang’s ruling family.

A day earlier, acting President Hwang Kyo-ahn also alerted cabinet members of Pyongyang’s terrorism attacks against South Korea and North Korean defectors in Seoul. The National Intelligence Service has reportedly beefed up security for high-profile defectors.

Kim Jong-nam, 46, died last week after being attacked by two women who coated their hands with toxic liquid then rubbed it on Kim’s face, according to the Malaysian police. The two women were arrested days after Kim’s death and told the police they thought the attack was a part of a “comedy prank.”

So far, the police have identified a total of eight North Koreans suspected of being linked to the killing. Having taken one into custody, they are searching for the seven others, although four are believed to have fled Kuala Lumpur shortly after the attack and are now believed to be back in Pyongyang.

Among the remaining three are a senior diplomat at the North Korean Embassy and an employee of North Korean state-owned airline Air Koryo, according to the Malaysian police. Both officials were in Malaysia, but they could not confirm if they were at the North Korean Embassy, the police said.

The death of Kim Jong-nam has escalated into a diplomatic row between North Korea and Malaysia, with the Southeast Asian country recalling its ambassador from Pyongyang after the regime’s ambassador in Kula Lumpur questioned the impartiality of the investigation into Kim.

Earlier in the day, an unidentified official at the North Korean Embassy told reporters they would reject the Malaysian police’s investigation results, saying that it was “all lies and slander.” They were scheduled to hold a press conference on the same day, but canceled at the last minute.

Describing Kim Jong-nam as “a citizen of the DPRK” who was travelling on a diplomatic passport, the KCNA criticized the Malaysian government for conducting a postmortem without its permission, saying it was “a wanton human rights abuse and an act contrary to human ethics and morality.”

The regime also denounced Malaysia’s refusal to hand the body back to North Korean officials, saying the decision “proves that the Malaysian side is going to politicize the transfer of the body in utter disregard of international law and morality and therefore serve a sinister purpose.”

By Yeo Jun-suk (jasonyeo@heraldcorp.com)