Three suspects detained in connection with the alleged murder of a man thought to be Kim Jong-nam should be "immediately released," the North Korean embassy in Malaysia said on Wednesday.
The embassy statement followed a claim by Malaysian police that North Korea was not offering assistance in its probe.
The "innocent" Vietnamese woman, Indonesian woman and North Korean man have been "arrested unreasonably," the embassy said.
Kim Jong-nam is the estranged half-brother of North Korean leader Kim Jong-un. Malaysian authorities allege that two women poisoned him at Kuala Lumpur International Airport on February 13. He died en route to hospital.
The North Korean embassy ridiculed the police account of the man's death saying the suspects could not have survived the alleged attack.
If the toxins were on their hands then how is it possible that these female suspects could still be alive? - North Korean embassy in Malaysia
Malaysian police said the women washed their hands soon after poisoning Kim.
Earlier on Wednesday, Malaysian police said a senior official in the North Korean embassy and a staffer at its state airline were also wanted for questioning over the death.
Malaysian police chief Khalid Abu Bakar said that investigators were not receiving assistance from the North Korean embassy in their hunt for four more suspects who they believe fled Malaysia immediately after the alleged assassination.
North Korea denies that the dead man is Kim Jong-nam.
On Monday, North Korean ambassador to Malaysia, Kang Chol, said the police investigation could not be trusted because the embassy had only ever identified the victim as Kim Chol, based on a passport carried by the dead man.
Malaysia has carried out an autopsy on the body, but has not released the results. Authorities say they will not release the body into North Korean custody before Kim Jong-nam's next-of-kin provide DNA samples to confirm whether the dead man is the half-brother of the DPRK's current leader.
Kuala Lumpur-based Nithyanantham Sivananthan, a council member of the International Criminal Bar, told TRT World, "There is a lot of speculation that it is him (Kim). From the legal perspective, until they (Malaysian authorities) have DNA comparison or positive identification that it is in fact the same man, I don't think the authorities are in a position to say for certain."