Interpol has issued a red notice, the closest to an international arrest warrant, for four North Koreans wanted in connection with the death of the estranged half-brother of North Korean leader Kim Jong-un.

Malaysian police requested Interpol's help to apprehend the suspects last month.

"We have obtained a red notice for the four North Korean nationals who were at the airport on the day of the incident and who have since left ... we are hoping to get them through Interpol," Khalid Abu Bakar, Malaysian police chief, announced on Thursday.

An Interpol red notice is a request to find and provisionally arrest someone pending extradition.

Kim Jong-nam was allegedly murdered on February 13, when Malaysian police say two women - an Indonesian and a Vietnamese - smeared super toxic VX nerve agent on his face at Kuala Lumpur International Airport.

The two women were charged with murder earlier this month, but police are looking for seven North Korean suspects in connection with the death, including four who are believed to have made their way back to Pyongyang.

The incident has resulted in a fierce diplomatic row between two countries with once strong ties.

North Korea has questioned the Malaysian investigation into the death and refused to acknowledge that the dead man is Kim Jong-nam.

Speaking at the North Korean embassy in Beijing at an unusual and hastily arranged news conference, Pak Myong-ho, a North Korean diplomat, blamed the United States and South Korea.

"The recent incident that occurred in Malaysia was clearly a political scheme by the US and South Korea aimed at hurting the DPRK's reputation and overthrowing the DPRK regime," Pak said, using the North's formal name, the Democratic People's Republic of Korea.

"The only parties that will benefit from this incident are the enemy countries."

WATCH: North Korea-Malaysia diplomatic dispute - THE STREAM

Pak made the comments to a hand-picked audience of reporters in a small, sparsely decorated room inside the embassy.

At the time of his death, Kim was carrying a diplomatic passport bearing another name, but Malaysian authorities said on Wednesday that his identity had been confirmed using DNA samples taken from one of his children.

Malaysia has also refused demands by the North Korean government for Kim Jong-nam's body to be released, saying that the remains can only be handed over to the next-of-kin under local laws.

No family member has come forward to claim the body.

State news agency Bernama, quoting Noor Rashid Ibrahim, Malaysian deputy police chief, as saying on Thursday that the family had given consent for Malaysia to manage Kim Jong-nam's remains.

Noor Rashid did not say when or where the consent was given.

Kim Jong-nam had been living in the Chinese territory of Macau under China's protection after the family went into exile several years ago.

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

He had been known to speak out publicly against his family's dynastic control of North Korea.

A man claiming to be the son of Kim Jong-nam appeared in video footage last week, saying he was lying low with his mother and sister.

An official at South Korea's National Intelligence Service confirmed the man in the video was Kim Han-sol, the 21-year-old son of Kim Jong-nam.

Malaysia is one of the few countries outside China that has for decades maintained ties with North Korea.

But as relations soured, Malaysia recalled its envoy from Pyongyang and expelled the North Korean ambassador.

North Korea then barred nine Malaysians - three diplomats and their six family members - from leaving the country, prompting Najib Razak, Malaysian prime minister, to describe the action as "hostage taking".

Malaysia followed with a tit-for-tat action stopping North Koreans from leaving.

Najib said Malaysia will begin formal negotiations with North Korea "when the time is right", clarifying previous reports saying that talks between the two countries had begun on Monday.