UN Secretary-General Antonio Guterres said late Friday he is "deeply troubled" by the confirmed death of Saudi journalist Jamal Khashoggi.

His remarks came after Saudi Arabia admitted Khashoggi was killed after a brawl inside its consulate in Istanbul. Khashoggi had been missing since early October after entering the diplomatic building.

"The Secretary-General is deeply troubled by the confirmation of the death of Jamal Khashoggi," said Stephane Dujarric, Guterres’s spokesman. "He extends his condolences to Mr. Khashoggi’s family and friends."

Guterres "stresses the need for a prompt, thorough and transparent investigation into the circumstances of Mr. Khashoggi’s death and full accountability for those responsible," said the statement.

Preliminary investigations carried out by the Public Prosecution Office revealed that Khashoggi had "a quarrel and brawl with the persons he met" at the consulate, which "resulted in his death", the state-run Saudi Press Agency said in a statement.

The agency reported that 18 Saudi citizens have been arrested over links to Khashoggi’s death and those having such links will be held accountable and brought to justice. (Anadolu)