As diplomatic tension escalates over the murder of Kim Jong-nam, Prime Minister Najib Abdul Razak has criticised North Korean ambassador to Malaysia Kang Chol over the latter's remarks.

"The statement by the ambassador was totally uncalled for. It was diplomatically rude. But Malaysia will stand firm," he was quoted as saying by Reuters.

According to an Astro Awani report, Najib stressed that Malaysia would not become a pawn for other countries.

He said Malaysia is a sovereign nation with its own constitution.

"We will not be pressured into making a decision on the murder of Kim Jong-nam. We will not be a pawn of other countries in defending our sovereignty," he added.

At a press conference in Kuala Lumpur yesterday, Kang Chol said Pyongyang distrusts the investigations by Malaysian authorities, and suspects the existence of hidden hands in the matter.

He also accused the Malaysian police of breaching human rights when raiding the condominium of a North Korean citizen in Kuala Lumpur in relation to the murder.

Kang Chol claimed that the police had threatened the suspect's family at gunpoint, and assaulted his son.

Minister: Don't question our forensics team

South Korea's Ministry of Unification rejected North Korea's claim that Malaysia colluded with Seoul in investigating the death, reports Bernama, quoting South Korea's Yonhap news agency.

Meanwhile, Bernama also reported Health Minister S Subramaniam saying that foreign countries should not dispute the expertise and capabilities of Malaysia's forensic team to conduct the post mortem on Jong-nam.

He said Malaysia has a highly qualified forensic team with vast experience in the field that had provided its expertise to solve various cases within and outside the country.

Jong-nam died on Feb 13 after being smothered with a cloth purportedly laced with an unidentified chemical by a woman at KLIA2.

Police have since arrested the woman, a Vietnam passport holder, as well as another woman who holds an Indonesian passport.

Police have also detained the second suspect’s boyfriend as well as arrested a North Korean citizen. Cops are looking for four more North Korean nationals who are believed to have fled the country.