Saudi authorities are refusing to confirm the whereabouts of Saud al-Qahtani, the former top aide to Saudi Crown Prince Mohammed bin Salman (MBS), according to the Washington Post.

Qahtani was fired in October, just days after the gruesome murder of Saudi journalist Jamal Khashoggi came to light.

In November, the Kingdom confirmed that he was under investigation and banned from leaving the country. Since then there has been no official statement in the case, the Washington Post reported.

Saudi prosecutors allege that Qahtani played a major role in Khashoggi's killing inside the Saudi consulate in Istanbul on October 2 last year. He was among 17 Saudis sanctioned by the US government over the murder.

Saudi officials say Prince Mohammed was not aware of the plot to kill Khashoggi, the Washington Post reported.

The US and western countries are watching the Saudi government's treatment of Qahtani as a measure of its seriousness in bringing to justice Khashoggi's killers, the paper reported.

A number of questions remain to be answered about Qahtani's involvement, including his role in planning the killing or whether he was framed.

Khalil Jahshan, executive director of the Arab Centre of Washington, told Al Jazeera that Qahtani's disappearance is a "natural progression of [Saudi Arabia's] investigation" and is likely used as a strategy to keep MBS protected from accusations regarding Khashoggi's murder.

"They have sheltered some of the key players accused of being involved [in the murder] whether by Turkey or by the international community," Jahshan said.

"The intention of the Saudi campaign right now is to keep the crown prince clear of any accusations with regards to the murder of Khashoggi."

'They are above the law'

Abdulaziz Almoayyad, Saudi human rights activist told Al Jazeera from Ireland that his disappearance is simply "what is expected from Saudi ideology".

Almoayyad said that non-violent Saudi dissidents who are asking for some reforms from the government are punished with capital punishment.

"They don't even need to be a reformer. This is the way the government deals with different opinions, to deal with people who ask for peoples representation," Almoayyad said, adding that the perpetrators of the murder won't be brought to justice.

"[MBS] isn't willing to punish [the murderers]; he isn't willing to punish his own and that will lead him to lose his power.

"In Saudi Arabia, this is a small minority that controls the people ... Saudi people are fighting for their rights and they are imprisoned for it.

"But this small circle [of MBS] cannot be harmed. They are super rich, super powerful and they really think they are above the law of Saudi Arabia, or international."

Last November, the CIA concluded that MBS ordered the assassination of Khashoggi in Istanbul, a finding that contradicts Saudi government assertions that Prince Mohammed was not involved.

US officials expressed high confidence in the CIA assessment, according to the Washington Post.