Australian authorities have approved a request from Malaysia to extradite a former prime ministerial bodyguard convicted of the murder of a Mongolian translator in a scandal that dogged Najib Razak’s time in office and transfixed the nation, the Guardian has learned.

A source said the Malaysian government had recently approached Australia to request that Sirul Azhar Umar be brought back to Malaysia, and that the plan had been given the green light after Malaysia agreed to cover the costs. It is believed Sirul will leave Australia within a month.

Any decision to return Sirul to Malaysia may suggest that the newly elected Malaysian government could be considering re-opening the case of Altantuya Shaariibuu’s death. Australia had previously refused to send Sirul back to Malaysia because he is facing the death penalty but it is understood that the Malaysian authorities have assured them he will receive fair treatment on his return.

Time running out for Malaysian hitman in Australia Read more

Altantuya had allegedly been the lover of Najib’s close confidant Abdul Razak Baginda, and had begun demanding money from Baginda for her role in a government deal to buy French submarines, where Baginda had allegedly been given multimillion-euro kickbacks.

In October 2006, the pregnant Altantuya was abducted in front of Baginda’s Kuala Lumpur home and taken to a forest in Subang where she was shot twice with a semi-automatic weapon and her body was blown up with military-grade explosives.

Sirul and and a fellow bodyguard, Azila Hadri, were charged with the murder and sentenced to death in 2009 but Sirul has denied carrying out the killing, saying that he was acting on orders from his superiors and was only involved in driving Altantuya to the scene. He alleged that Hadri was the one who murdered Altantuya. No motive for the killing was ever established and key witnesses were never called in the trial.

Facebook Twitter Pinterest Mongolian model and translator Altantuya Shaariibuu Photograph: HANDOUT/EPA

Sirul escaped to Australia in 2014 while out on bail during an appeal against his conviction. He was put on Interpol red alert and arrested in Queensland for overstaying his tourist visa. He has been held in the Villawood detention centre in Sydney ever since.

After Najib was ousted in the election in May, there have been multiple calls on the new government, led by Mahathir Mohamad, to reopen the investigation into Altantuya’s murder and the possible implication of Najib, his wife Rosmah Mansor and Baginda.

The recently released Anwar Ibrahim was among those who had called for Sirul to be brought back to Malaysia. Last week he called for a new trial “that’s clearly transparent”. “You have to allow for due process to take place and Malaysian authorities may seek Australia’s cooperation just to make sure there’s a fair trial,” he said.

The Australian immigration minister, Peter Dutton, was contacted for comment but had not responded at the time of publishing. The attorney general’s office, which is responsible for extraditions, released a statement saying “the Australian government does not comment publicly on extradition matters”.

However, the Australian high commission in Kuala Lumpur later on Friday released a statement saying: “The Australian government confirms that discussions have been held with the Malaysian government clarifying the situation of Mr Sirul Azhar Umar.” The statement said no extradition request from Malaysia had been received by the Australian authorities.

A spokesman for the Malaysian government said “it is classified information and we can not comment on it.”