The Istanbul governor's office has put Hatice Cengiz, the fiancée of slain Saudi journalist Jamal Khashoggi, under 24-hour police protection, Anadolu news agency reported, citing security officials.
The Turkish authorities did not explain their reasons for taking the decision.
Ms. Cengiz was the last to see Khashoggi before he entered the Saudi consulate building in Istanbul on 2 October, where he was killed and dismembered. Having initially claimed that Khashoggi left the building unharmed, Saudi Arabia claimed on Friday that Khashoggi died after a fistfight with people he met at the consulate.
On Sunday, Saudi Foreign Minister Adel Al-Jubeir described Khashoggi's assassination as "tremendous mistake," saying the Saudi authorities are determined to uncover the circumstances of his death. He explained: "We are determined to uncover every stone. We are determined to find out all the facts. And we are determined to punish those who are responsible for this murder.