"For an investigation to be carried out free of any appearance of political considerations, the involvement of international experts, with full access to evidence and witnesses, would be highly desirable," Michelle Bachelet said in a statement.
Khashoggi, a 59-year-old Saudi journalist and Washington Post contributor, was killed after entering the Saudi consulate in Istanbul on October 2 to obtain paperwork ahead of his upcoming wedding. His body has not yet been found.
His death has brought near unprecedented international scrutiny on Saudi Arabia and its powerful Crown Prince Mohammad bin Salman. The journalist's fiancee has accused the regime of a massive cover-up.
Bachelet stressed the importance of ensuring the murder be investigated in an independent and impartial manner.
"I welcome the steps taken by Turkish and Saudi authorities to investigate and prosecute the alleged perpetrators of Mr. Khashoggi's murder," the UN High Commissioner for Human Rights said.
"But given the information that high-level officials in Saudi Arabia were apparently involved, and it took place in the Consulate of Saudi Arabia, the bar must be set very high to ensure meaningful accountability and justice for such a shockingly brazen crime against a journalist and government critic," she insisted.
Bachelet added that it was important to determine whether "serious human rights violations such as torture, summary execution or enforced disappearance were committed and to identify all those implicated in this crime, irrespective of their official capacity."
She called on authorities in both Turkey and Saudi Arabia to cooperate in ensuring that the full truth about Khashoggi's murder comes to light.
"Forensic examination, including an autopsy on the body of the victim is a crucial element in any investigation into a killing, and I urge the Saudi authorities to reveal the whereabouts of his body without further delay or
prevarication," she said.
Bachelet's statement marks the third time she has commented on Khashoggi's disappearance and murder.
It comes after Turkish President Recep Tayyip Erdogan called on Saudi Arabia's chief prosecutor, who visited the consulate in Istanbul Tuesday, to find out who ordered the journalist's murder, and not spare "certain people" in his investigation.
Saudi Arabia is seeking to draw a line under the crisis after offering a series of differing narratives following the journalist's disappearance.
Since admitting the murder was premeditated, the Saudi leadership has blamed a "rogue operation" for the killing of Khashoggi, who was once an insider in Saudi royal circles and had lived in self-imposed exile in the
United States since 2017.