A Malaysian court postponed a hearing for two women accused of killing North Korean leader Kim Jong-un's half-brother at Kuala Lumpur airport earlier this year.

Kim Jong-nam died after the two women attacked him at Kuala Lumpur International Airport in February as he prepared to board a flight to Macau.

The hearing, which had been scheduled for Thursday morning, was postponed to May 30 after defence lawyers complained about lack of access to police evidence, including CCTV footage and the suspects' mobile phones.

Wearing bullet-proof vests, Indonesian Siti Aisyah, 25, and Doan Thi Huong, 28, from Vietnam, were to a heavily guarded magistrate's court near the airport where Kim Jong-nam was fatally poisoned on February 13.

One of their lawyers warned they feared "a trial by ambush" with police not sharing evidence.

Police accuse the pair of having wiped the banned nerve agent VX on Kim's face at the airport.

US and South Korean officials say the murder was orchestrated by the North's leader Kim Jong-un.

Kim Jong-nam, the eldest son of the late North Korean leader Kim Jong-il, had spoken out publicly against his family's dynastic control of the isolated, nuclear-armed nation.

Pyongyang denies the accusation, insisting he died of a heart attack.

READ MORE: Who produced the VX poison that killed Kim Jong-nam?

Lawyers for Aishah and Huong told the Malaysian magistrate court that police had not responded to requests to provide evidence, including CCTV recordings and statements from three North Korean suspects that were allowed to leave the country.

The three suspects returned to Pyongyang along with the body of Kim Jong-nam as part of a swap deal with North Korea, which had banned nine Malaysians from leaving the country in a diplomatic spat.

"We've lost an opportunity to cross-examine them," Aishah's lawyer Gooi Soon Seng told reporters outside the court. "There should be no trial by ambush."

Malaysian police have identified four other North Koreans as suspects. They are believed to have left Kuala Lumpur for Pyongyang on the day of the killing.

About 100 police officers, include commandos in balaclavas and carrying assault rifles, guarded the court compound during the women's appearance.

The case is due to be transferred to an upper court where the women will be tried for murder. If convicted, they could face the death penalty, which is carried out by hanging in Malaysia.

Aisyah and Huong have told diplomats from their countries that they had believed they were carrying out a prank for a reality television show, and not a murder.

Tran Huy Hoang, a young Vietnamese man who attended the hearing and described himself as a cousin of Doan, told AFP news agency "she loves to travel and party but she never do anything violent".

"All of us believe she was cheated," he said.