PETALING JAYA (The Star/Asia News Network) - Prime Minister Najib Tun Razak is not involved in the murder of Mongolian translator Altantuya Shaariibuu, his predecessor Tun Abdullah Ahmad Badawi said in a statement on Friday.

Abdullah's comments came amid calls by former Prime Minister Mahathir Mohamad for an investigation be conducted into the case.

Abdullah said the investigation into the 2006 murder was concluded during his tenure as prime minister.

"Among the matters reported to me during my time as prime minister was the result of the investigation of the murder of Mongolian Altantuya Shaariibuu," Abdullah said in his statement.

"Based on the findings from the thorough investigation conducted by the Royal Malaysian Police that was conveyed to me, it was confirmed that Datuk Seri Najib Tun Razak is not involved at all in the case," he said.

Altantuya was murdered on Oct 18, 2006 and her remains were found in a forest near Puncak Alam, Shah Alam. She was believed to have been killed because she knew details about alleged kickbacks in a major defence deal.

Two Najib bodyguards, Sirul Azmar Omar and Azilah Hadri, were charged with murdering Altantuya in 2006 and convicted by the High Court in 2009.

They were freed after the appellate court acquitted them in 2013, but the Federal Court reversed the acquittal in January and sent them back to hang.

Sirul fled to Australia last year and is being held in an immigration detention centre. He said in February he was ordered by "important people" to kill Altantuya.

Australia has said it will not turn Sirul over to Malaysia unless Kuala Lumpur gives assurances he will not be executed.