Prime Minister Najib Abdul Razak doesn't have to prove his innocence in the murder case of Altantuya Shaariibuu as it is up to the the courts to prove him guilty, said a minister.

Communications and Multimedia Minister Salleh Said Keruak also pointed out that the courts had already exonerated Najib's associate Abdul Razak Baginda with regards to the case.

"So in what other way is Dr Mahathir Mohamad suggesting that Najib clear his name? Is there another method other than through the courts?" he asked in a blog posting today.

Salleh was responding to Mahathir's earlier blog post today urging Najib to prove false several allegations made in a recent Al-Jazeera documentary which implicated the prime minister.

“Proof must be given that the murder, cover-up, the police involvement were not true and that Abdul Razak Baginda was in no way guilty of the terrible crime," the former premier had said.

Salleh (photo) said by questioning the court's decision on the Altantuya murder, Mahathir could be committing contempt of court.

"Is Mahathir saying that the Malaysian courts cannot be trusted and that Malaysian judges are crooked?

"If not why is Dr Mahathir questioning the court and is insinuating that the court is not honest?" he asked.

Najib has repeatedly denied being involved in the 2006 murder case which is often exploited by political rivals during election campaigns.

The prime minister’s close associate Razak Baginda was initially charged with abetting the murder, but was acquitted without being called to make his defence.

Two former special operations force personnel Sirul Azhar Umar and Azilah Hadri have been convicted with murdering the Mongolian national.

Part of conspiracy claim

However, Sirul fled to Australia before the Federal Court overturned his acquittal in January. He is currently being held at an immigration detention centre in Sydney.

The Al Jazeera documentary alleged, among others, that Sirul was attempting to blackmail Najib and quoted an unnamed relative of the former policeman as claiming that Razak Baginda was the one who pulled the trigger on Altantuya.

Inspector-general of police Khalid Abu Bakar dismissed latest allegations and announced that police are investigating Al Jazeera's Australian-based journalist Mary Ann Jolley over her report and those who fed her the information.

Najib has claimed the documentary was part of conspiracy to force him out of office.