Malaysian police are investigating whether the VX nerve agent used to kill Kim Jong Nam, the estranged half-brother of DPRK leader Kim Jong Un, was brought into the country or produced in Malaysia, the country's police chief said on Friday.

"We are investigating it," Khalid Abu Bakar told a press conference. "If the amount of the chemical brought in was small, it would be difficult for us to detect," he added.

Traces of VX, listed as a weapon of mass destruction by the United Nations, were detected after swabs were taken from the dead man's face and eyes, police said, citing a preliminary report from the government's chemical weapons analysis unit.

Scientists continued to analyze "other exhibits" from the autopsy, Khalid also said.

The police chief added that one of two women suspected of killing Kim Jong Nam with the nerve agent had also suffered its effects. 

Kim Jong Nam died on February 13 at Kuala Lumpur International Airport 2 after being approached by two women who appeared to wipe something in his face.

Malaysian detectives are holding three people: two women from Indonesia and Vietnam, and a DPRK man. 

They want to speak to seven others, four of whom are believed to have fled to Pyongyang on the day of the attack.

Malaysia's police chief said the woman who ambushed Kim clearly knew she was carrying out a poison attack, dismissing claims that she thought she was taking part in a TV prank.

The DPRK’s state media broke a 10-day silence on the incident on Thursday, blaming Malaysia for its "immoral" handling of the case and accusing it of playing politics with the body. 

The DPRK still has not acknowledged that the victim is the estranged brother of leader Kim Jong Un, calling him only "a citizen" of the DPRK "bearing a diplomatic passport".

The only known use of VX is as a chemical warfare agent, according to the US Centers for Disease Control and Prevention (CDC) which describes it as “the most potent of all nerve agents,” both odorless and tasteless.

Symptoms can appear within seconds of a person being exposed to VX in vapor form and minutes if it’s in liquid form. Symptoms include blurred vision, coughing, headaches and nausea in low doses, but can lead to paralysis, loss of consciousness and respiratory failure in bigger amounts, according to the CDC. 

Rohan Gunaratna, head of the Singapore-based International Centre for Political Violence and Terrorism Research, was quoted by AFP news agency as saying the DPRK has manufactured VX in the past.

He said it would not have been difficult to smuggle VX into Malaysia in a diplomatic pouch, thereby bypassing regular customs checks. 

(With inputs from Reuters, AFP)