ANKARA (Reuters) - An adviser to Turkish President Tayyip Erdogan said on Sunday he believed prominent Saudi journalist Jamal Khashoggi, who has been missing for six days, was killed in the Saudi Arabian consulate in Istanbul.

Yasin Aktay, who advises Erdogan in his ruling AK Party, also told Reuters that Turkish authorities believed a group of 15 Saudi nationals were “most certainly involved” in the matter, and added that statements by Saudi officials on the absence of camera records were not sincere.

Late on Saturday, Turkish sources told Reuters that Turkish authorities believed Khashoggi had been killed inside the consulate last week, in what they described as the deliberate targeting of a prominent critic of the Gulf kingdom’s rulers.