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.
READ: Turkish staff of Saudi consulate give statements in Khashoggi probe
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.