North Korea denied that its agents masterminded the assassination of the half-brother of leader Kim Jong-un, saying a Malaysian investigation into the death of one of its nationals is full of "holes and contradictions".

The North's response on Thursday came a day after Malaysian police said they were seeking two more North Koreans, including the second secretary of North Korea's embassy in Kuala Lumpur, in connection with the February 13 killing of Kim Jong-nam at a Malaysian airport.

Malaysia police have not directly pinpointed North Korea as being behind the death, but have already arrested a North Korean man working at a Malaysian company along with three other Southeast Asian people. They are searching for several more North Koreans.

READ MORE: Kim Jong-nam's killing one week on - What we know

The Korean Jurists Committee, a legal body affiliated with North Korea's rubber-stamp parliament, said in a statement that the Malaysian investigation lacks fairness and was influenced by the South Korean government, which blames Pyongyang for the death.

The North has not acknowledged that the dead man is Kim. Thursday's statement described the man only as a North Korean citizen bearing a diplomatic passport.

It said that South Korea had "kicked up a fuss" and had plotted to have North Korea blamed for the killing.

North blames Malaysia

"The biggest responsibility for his death rests with the government of Malaysia as the citizen of the DPRK died in its land," the statement said.

The DPRK refers to the Democratic People's Republic of North Korea, the country's official name.

Malaysian police said on Wednesday that the two women suspected of fatally poisoning Kim were trained to coat their hands with toxic chemicals and then wipe them on his face.

Police say the substance used remains unknown, but it was potent enough to kill Kim before he could make it to a hospital.

Inspector-General of Police Khalid Abu Bakar told reporters that the women, one Vietnamese and the other Indonesian, knew they were handling poisonous materials and "were warned to take precautions".

The women and a Malaysian man, believed to be the boyfriend of the Indonesian woman, have been arrested.

Surveillance video showed both women keeping their hands away from their bodies after the attack, he said, then going to restrooms to wash.

Those details are not clear in video obtained by media outlets.

Kim Jong-nam killing: Two North Koreans sought by police

But the North Korean embassy in Kuala Lumpur has already ridiculed the police account and demanded the immediate release of the two "innocent women."

An embassy statement asked how the women were able to survive if they also had the deadly toxins on their hands.

Malaysian police said the women washed their hands soon after poisoning Kim.

'A planned thing'

Khalid said the women had practised the attack at two Kuala Lumpur malls. "We strongly believe it is a planned thing and that they have been trained," he said.

Khalid couldn't confirm whether North Korea's government was behind Kim's death but added: "What is clear is that those involved are North Koreans."

At least one of the women has said she was tricked into attacking Kim, believing she was taking part in a comedy prank TV show.

The case has perplexed toxicologists, who question how the two women could have walked away unscathed after handling a powerful poison.

Kim had spent most of the past 15 years living in China and Southeast Asia. He is believed to have had at least three children with two women. No family members have come forward to claim the body.

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South Korea's spy agency believes North Korea was behind the killing, but has produced no evidence.

Analysts in Seoul said Kim Jong-un probably had his brother killed because he could be a potential challenger to his rule in a country where his family ruled for three generations and where the bloodline is still extolled in the country's founding mythology.

North Korea has a long history of ordering killings of people it views as threats to its regime.

While Kim was not thought to be seeking influence, his position as eldest son of the family that has ruled North Korea since its founding could have made him appear to be a danger.

He was at the airport to fly to Macau, where he had a home.

Source: AP news agency