"At the moment there are certain people who arrived from Saudi Arabia".
Saudi Arabia's consul-general in Istanbul gave local staff the day off last Tuesday, when Mr Khashoggi vanished, according to Turkish media.
"This will be a file between Saudi Arabia and us", the Turkish official warned.
"The initial assessment of the Turkish police is that Mr. Khashoggi has been killed at the consulate of Saudi Arabia in Istanbul". The ministry did not say when the premises would be searched.
"We are hoping against hope that Mr Khashoggi is unharmed and will soon return to his writing desk", the Post said.
Killing someone such as Khashoggi - who long had ties to the royal family and the Saudi intelligence apparatus - in a consulate would be a major escalation in the prince's rise. Security camera footage shows boxes being loaded into the van, which carried diplomatic number plates.More news: Saints outpace Redskins on MNF
However, a number of closed-circuit surveillance cameras surround the area.
Reuters' Turkish sources did not say how they thought Khashoggi was killed.
She raised the alarm four hours later, by which time the convoy is believed to have left the consulate.
Fred Hiatt, director of The Washington Post's editorial page, issued a statement calling Khashoggi's possible murder a "monstrous and unfathomable act".
"Our country's values should be and must be a cornerstone of our foreign policy with foes and allies alike", he added.
The 59-year-old former government adviser visited the consulate on Tuesday to obtain paperwork to marry his Turkish fiancee, Hatice Cengiz, who was reportedly waiting outside the building for him.
He has also criticized Saudi Arabia's role in Yemen, where Riyadh leads a military coalition fighting alongside the government in its war with Iran-backed rebels.More news: Liveblog: Google’s Pixel 3 launch event at 11am ET Tuesday, October 9
"If the crown prince does not respond with full cooperation, Congress must, as a first step, suspend all military cooperation with the kingdom", the Post said. Saudi Arabia claimed that Khashoggi had left the embassy without anyone noticing. "It is (the duty) of the consulate officials", Erdogan said during a visit to Hungary. Then why do you not prove this?
Turkish Foreign Ministry spokesman Hami Aksoy said the investigation was "continuing intensively", and that the Vienna Convention allowed for consulates to be searched by the authorities of the host country with the consent of the mission chief.
There was no immediate comment on the report from the Saudi authorities.
From the beginning, Turkey has been highly critical of the blockade and has helped Qatar by sending troops to Qatar in support, and by increasing trade with Qatar, circumventing the blockade. Fearing for his life, Khashoggi has lived in self-imposed exile in the United States for the a year ago.
"You would hope that the United States would at least start asking very serious questions about what was going on, and press the Saudis for answers", Ivo Daalder, a former USA envoy to North Atlantic Treaty Organisation, told CNN. I don't like hearing about it. "Hopefully, that will sort itself out", Trump told reporters at the White House on Monday. Right now nobody knows anything about it, but there are some pretty bad stories going around. "I do not like it". "Saudi Arabia wasn't always this repressive".More news: Chaser projects Alan Jones’ ad and phone number onto Sydney Opera House