KUALA LUMPUR: North Korea's Ambassador to Malaysia Kang Chol (pic) continued his criticism of Malaysia's handling of Kim Jong-nam's murder, threatening to plunge the two countries into a diplomatic row.

Kang accused Malaysian police of threatening the family of a North Korean citizen with guns, and also beating up the man's teenage son when they raided his condominium in Kuala Lumpur.

This comes after Malaysia recalled its ambassador to North Korea, as well as Kang himself being summoned to Wisma Putra on Monday morning.

"Last Friday night, Malaysian plainclothes police raided the condominium of our citizen here in Kuala Lumpur and forcibly arrested him without any warrant or evidence," Kang said.

"They even pointed guns at his family members to threaten their lives and beat his teenage son in the face.

"This is the human rights abuse that can be seen only in US gang films," he told a press conference in front of the North Korean Embassy on Monday afternoon.

He was referring to the arrest of Ri Jong-chol from Pyongyang, 47, the fourth person to be arrested in the investigation into the death of Jong-nam.

Wisma Putra, in a strongly worded response, said it viewed Kang's "baseless allegations as a serious attempt to tarnish the country's reputation."

This statement was issued as Kang was still in the Foreign Ministry building here to meet Deputy Secretary-General 1 Raja Nurshirwan Zainal Abidin.

Kang had earlier accused Malaysia of colluding with South Korea, saying that North Korea could not trust the investigation results of Malaysian police, nor could it trust statements by Malaysian officials.

However, Malaysian Prime Minister Datuk Seri Najib Tun Razak defended the work of Malaysian police and doctors, saying they were "very professional."

"I have absolute confidence that they are objective in whatever they do.

"We will be objective and expect them (North Korea) to understand that we apply the rule of law in Malaysia," Najib told reporters after launching the Religion and Civilisational Sustainability international conference here Monday.

Despite his accusations, Kang also called for a joint-investigation into the death of Jong-nam, the half-brother of North Korean leader Kim Jong-un.

"We officially inform Malaysia and the international community that we suggest a joint-investigation on this incident for (greater) clarification," he said.

He added that if Malaysia agreed with his proposal, North Korea was prepared to send a delegation of lawyers to assist.

Jong-nam, 45, was killed by two women who splashed his face with a chemical at the Kuala Lumpur International Airport 2 (KLIA2) departure hall on Feb 13. He was about to leave for Macau.

Malaysian police have also arrested Doan Thi Huong, who holds a Vietnamese passport, and Siti Aisyah from Indonesia, and have detained the latter's boyfriend to assist with investigations.