Malaysian prosecutors on Thursday rejected a request from the remaining defendant in the murder trial of Kim Jong Nam, the estranged half-brother of North Korea's leader, to drop the charge against her.

Lead prosecutor Mohamad Iskandar Ahmad told the Shah Alam High Court in the outskirts of Kuala Lumpur that the attorney general gave the order to "proceed with the case" against 30-year-old Vietnamese national Doan Thi Huong.

Huong's co-accused, Indonesian woman Siti Aisyah, 27, was released on Monday after prosecutors unexpectedly withdrew the murder charge against her. She has already returned home to Indonesia.

"We are clearly disappointed with the decision of the attorney general not to withdraw the charge against Doan Thi Huong," Huong's lead counsel Hisyam Teh Poh Teik told the court.

He called the decision "perverse" and said it "does not speak well of our criminal justice system."

He added there was "discrimination" considering that the court had found that both women had a case to answer at the end of the first stage of their trial.

Judge Azmi Ariffin made that ruling last August based on the testimony of 34 witnesses and airport security camera footage tendered by the prosecution. He ordered the women to mount a defense against what he said was a "well-planned conspiracy" hatched with four North Korean suspects.

Hisyam argued that Aisyah and Huong mounted the same defense strategy, that they both thought they were taking part in a prank video and that they both were made "scapegoats" by the North Koreans.

(Kim Jong Nam pictured in February 2007.)

"It is our complaint that the public prosecutor has not acted fairly and justly toward Doan Thi Huong," he told the court.

Undaunted, Hisyam later told reporters Huong will make a second application to the attorney general to reconsider his decision.

In the meantime, the Vietnamese government has begun campaigning to push the Malaysian government to release its citizen.

"Substantive efforts are being made now to secure her release," Hisyam told the court about the efforts spearheaded by the Vietnamese Justice and Foreign ministries.

Malaysian Foreign Minister Saifuddin Abdullah confirmed on Wednesday that he was contacted by his Vietnamese counterpart seeking his assistance on this matter.

"He called me at 6 p.m. (Tuesday) and asked me for a favor," he told reporters. "My reply was we will let the court decide."

The Vietnamese Foreign Ministry, quoting Foreign Minister Pham Binh Minh, tweeted late Tuesday that Minh "asked the Malaysian side to ensure fair judgement for Huong and to set her free."

The move by Hanoi follows revelations that Aisyah was freed as a result of successful lobbying by the Indonesian government.

(Siti Aisyah shakes hands with Indonesian President Joko "Jokowi" Widodo in Jakarta on March 12, 2019, after her release the previous day.)

Aisyah returned home the same day she was released and on Tuesday she had an audience with Indonesian President Joko "Jokowi" Widodo in Jakarta. Indonesian officials told reporters that Jokowi had earlier instructed that efforts be made to get her out of prison.

So far, the Malaysian attorney general has remained silent over the reasons for dropping the murder charge against Aisyah while maintaining it against Huong.

Iskandar merely told Kyodo News that "representations" were made on Aisyah's behalf and that "the decision was made based on the merits of those representations."

Huong was supposed to begin her testimony on Monday before the dramatic turn of events. She also could not take the stand on Thursday after the judge agreed that a clearly distressed and distraught Huong appeared not "mentally and physically fit" to testify.

Hisyam said Huong has not been sleeping well since Monday, at times only one hour a night.

The judge adjourned the hearing until April 1 to allow time for Huong to seek medical treatment.

At the end of the hearing, Huong was seen sobbing when Vietnamese Ambassador Le Quy Quyn spoke to her.

Both women were charged with killing North Korean leader Kim Jong Un's paternal half-brother by smearing the highly toxic nerve agent VX on his face at Kuala Lumpur International Airport on Feb. 13, 2017. They claimed that they thought they were taking part in a televised prank.

In their joint trial, which began in October 2017, the women pleaded not guilty.