Kuala Lumpur, Mar 14 (IANS): Malaysian prosecutors on Thursday rejected an appeal to drop a murder charge against one of the two women accused of using the deadly nerve agent VX to murder North Korean leader Kim Jong-un's half brother, just days after allowing her co-defendant to walk free.

The decision means that Doan Thi Huong of Vietnam will remain as the only suspect in the case still behind bars, CNN reported.

Huong was one of two women charged with the February 2017 murder of Kim Jong-nam, an offence punishable by hanging.

The other, Indonesian national Siti Aisyah, was freed on Monday in a surprise ruling.

Prosecutors did not reveal why they rejected Huong's appeal but let Aisyah go free.

Huong's legal team had petitioned prosecutors to release her on the same grounds as Aisyah, arguing it would be unfair to free one of the co-defendants but not the other.

However Huong told the media through an interpreter that she wasn't bitter Aisyah was freed and she was not.

"God knows me and Siti Aisyah didn't do anything," she said.

Hanoi's Ambassador to Malaysia Le Quy Quynh told CNN that the Vietnamese Justice Minister had sent a letter to Malaysia's attorney general requesting Huong's release.

He said Hanoi would again request that Malaysian authorities treat Huong fairly and release her "as soon as possible."

Judge Azmi Ariffin adjourned court on "humanitarian grounds", saying Huong appeared "not well".

The next hearing will take place on April 1.

Four North Koreans who fled Malaysia for an unknown destination shortly after the assassination were also charged in absentia with the murder. The Interpol has issued red notices asking governments to send them back to face trial.

North Korea has consistently denied involvement in the killing, though US, South Korean and Malaysian authorities have said Pyongyang was responsible.