Altantuya Shaariibuu was 28 and pregnant when she was fatally shot and blown up with military-grade plastic explosives in a jungle outside Kuala Lumpur in October 2006.

One of Najib's former bodyguards, who is on death row for the murder, has sought a retrial and made a sworn statement earlier this week alleging that Najib gave him an order to "shoot to kill" the Mongolian because she was a foreign spy. The bodyguard, Azilah Hadri, said in the statement, reported by local media, that Najib also told him to use explosives to dispose of her body. His allegation was the first to directly link Najib to the murder.

Najib, already beset by multiple corruption charges after his election ouster last year, has slammed Azilah's accusation as another plot by the new government to discredit and silence him.

"I have never directed anyone to kill a Mongolian citizen named Altantuya Shaariibuu. In fact, I have never met nor do I know the deceased," Najib said in his oath in a Kuala Lumpur mosque after Friday prayers. "Ïf I lied, may Allah's curse be upon me. If I am truthful, then may those who slander me be cursed by Allah."

Dozens of supporters cheered as Najib smiled with his wife Rosmah Mansor at his side. Najib is currently on trial on dozens of corruption charges linked to the multimillion-dollar looting of state investment fund 1MDB and has denied any wrongdoing.

Azilah and Sirul Azhar Umar, who were members of an elite police unit guarding Najib, were convicted of Altantuya's murder but Sirul fled to Australia while awaiting his appeal. The Mongolian's lover, Abdul Razak Baginda, a close aide to Najib, was tried but acquitted of abetting the crime. The mastermind and motive of the murder were never determined.

There was speculation that Altantuya, who was also working as a translator for Abdul Razak, was killed to keep her from exposing alleged corruption involving the purchase of submarines from France under Najib, who was then deputy premier and defense minister. Najib later became prime minister until his party lost power in a shocking defeat in May last year.

.The new government last year reopened investigations into her death following appeals from Altantuya's family. The other policeman, Sirul, has offered to return to Malaysia to provide evidence in the case if he is promised a pardon. Australia has said it won't extradite him because of Malaysia's death penalty.