Two women accused of assassinating the estranged half-brother of North Korean leader Kim Jong-un with a banned nerve agent pleaded not guilty at the start of a high-profile murder trial in a Malaysian court on Monday.

Indonesian Siti Aisyah, 25, and Doan Thi Huong, 28, a Vietnamese, are charged with killing Kim Jong-nam by smearing his face with VX - a chemical poison banned by the United Nations - at Kuala Lumpur's international airport on February 13.

The women told their lawyers they did not know they were participating in a deadly attack and believed they were carrying out a prank for a reality TV show.

Both women wore bullet-proof vests as they were led into the court on the outskirts of Malaysia's largest city. They face the death penalty if convicted.

Prosecutor Muhamad Iskandar Ahmad read a statement giving details of Kim's murder.

"The evidence clearly showed that their action to swipe the poison known as VX caused the death of the victim," he told the court.

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Defence lawyers said the real culprits have left Malaysia and the women's innocence will be proven in court.

They demanded the prosecution immediately name four other suspects who have also been charged in the case, but who are still at large. The prosecution said their identities would be revealed during the trial.

"A fair trial must include the right to know," Gooi Soon Seng, Aisyah's lawyer, told the court. "The charge must be clear, not ambiguous."

The women carried out several practice runs at shopping malls in Kuala Lumpur ahead of the attack on Kim, the prosecution said.

"The prank practice carried out by the first and second accused with the supervision of the four who are still at large was preparation to see through their common intention to kill the victim," the prosecution said in its charge sheet.

Aisyah was paid $100-$200 for each prank and hoped the income would allow her to stop working as an escort, Gooi said.

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South Korean and US officials have said Kim Jong-un's regime was behind the murder. North Korea denies the allegation.

The trial is expected to run until November 30 and the prosecution is expected to call up to 40 witnesses.

Kim, who was 45 or 46, was the eldest son of the family that has ruled North Korea since its founding, yet he reportedly fell out of favour in 2001 when he was caught trying to enter Japan on a false passport, saying he wanted to visit Tokyo Disneyland.

Robert Kelly, from Pusan National University in South Korea, said Kim's murder likely strained relations between allies North Korea and China, which had given him protection in its territory of Macau.

"The Chinese realise all this North Korean gangsterism - not just the murders but the traffic in methamphetamines and counterfeit dollars - I think the Chinese would like to rein that in," Kelly told Al Jazeera.