Saudi Arabia's ambassador to Turkey was on Thursday summoned to the foreign ministry after a prominent journalist critical of Riyadh went missing.
Saudi Arabia's Consulate General in Istanbul said in a statement on Wednesday that Khashoggi had left the consulate building shortly after his appointment on Tuesday. "If he had left the consulate as said by the Saudis, we would know where he is", she said. "I hope this issue will be resolved smoothly".
While Khashoggi's friends and well wishers say they fear for him, his current status has become a bone of contention between Saudi Arabia and Turkey, whose relationship has soured in the a year ago. The woman, who asked to be identified only as Hatice, said she waited for him until 1am, even after being told there was no one left inside the building, and then began alerting others to his disappearance. "We don't have information to the contrary".
Khashoggi has been living in self-imposed exile in the United States, and is an established critic of the Saudi government - particularly the reform plans championed by Crown Prince Mohammed Bin Salman.
On Oct. 2, Khashoggi entered the consulate to get paperwork he needed in order to be married next week, said his fiancee Hatice, who gave only her first name out of fear of retribution.
Turkish authorities have also said they believe Khashoggi is still there.
However, CBS News said it wasn't clear if Secretary of State Mike Pompeo raised the matter with Saudi Prince MBS during a conversation on Wednesday.
However, Turkey has avoided public criticism of Saudi Arabia, which is a regional economic power due to its oil wealth and which is also the home of Islam's two holiest shrines.
He said contacts were continuing to "overcome the problem".
Saudi Arabia's Istanbul consulate said Wednesday that it was investigating reports of Khashoggi's disappearance, according to the kingdom's official Saudi Press Agency.
Khashoggi is one of the rare Saudi journalists to raise his voice against repression in the country.
"It would be unfair and outrageous if he has been detained for his work as a journalist and commentator", the Post's worldwide opinions editor, Eli Lopez, said in a statement.
"I do not know what has happened to him".
As a journalist, he interviewed al-Qaeda leader Osama bin Laden several times in Afghanistan and Sudan, and served twice as editor of Al Watan newspaper.
Khashoggi maintained ties with Saudi elites and launched a satellite news channel, Al-Arab, from Bahrain in 2015 with the backing of Saudi billionaire Prince Alwaleed bin Talal.
Scores of businessmen were detained last November in Riyadh's Ritz-Carlton hotel in a separate campaign against corruption, unnerving some foreign investors.
Kalin raised concerns about the legality of the apparent detention, saying that Khashoggi's disappearance "has a dimension of worldwide law".
"If, as it claims, Saudi Arabia truly wishes to transition to a more open society, it will have to accept the fundamental rights of freedom of expression and freedom of the press", wrote Ravi R. Prasad, the institute's head of advocacy.
Reporters Without Borders said Khashoggi's disappearance was "extremely worrying", calling on Saudi and Turkish authorities "to do everything to ensure that this journalist reappears - free -- as soon as possible".