Turkish TV has aired video from CCTV said to show missing Saudi journalist Jamal Khashoggi entering the Saudi consulate in Istanbul.
Mr Khashoggi, a critic of the Saudi monarchy, visited on 2 October but failed to re-emerge.
Turkish security sources say they fear he was killed there. Saudi Arabia denies this.
The video also shows vehicles driving up to the consulate, including a black van thought central to inquiries.
Footage broadcast by Turkey’s TRT World channel also shows a group of men apparently passing through security at Istanbul airport.
Turkey’s Sabah newspaper reports that it has identified 15 members of an intelligence team it says was involved in the Saudi’s disappearance.
Mr Khashoggi was visiting the consulate to finalise his divorce so he could marry his Turkish fiancée Hatice Cengiz.
What has the international reaction been?
The UK’s foreign secretary has told Saudi Arabia that Britain expects urgent answers over the disappearance of Mr Khashoggi.
In a phone call to Saudi Arabian Foreign Minister Adel al-Jubeir, Jeremy Hunt warned that “friendships depend on shared values”.
Earlier on Tuesday, US President Donald Trump said he had not yet spoken to Saudi officials about the journalist’s disappearance.
“I have not but I will be at some point,” he told reporters.
US Secretary of State Mike Pompeo called on Saudi Arabia to “support a thorough investigation” of his disappearance and “to be transparent about the results”.
UN experts have demanded a “prompt independent and international investigation” into his disappearance.
Last week, Saudi Crown Prince Mohammed told Bloomberg News that his government was “very keen to know what happened to him”, and that Mr Khashoggi had left “after a few minutes or one hour”.
Crown Prince Mohammed’s brother and the Saudi ambassador to the US, Prince Khaled bin Salman al-Saud, has insisted all the reports about his disappearance or death “are completely false and baseless”.
How has Khashoggi’s fiancee reacted?
Hatice Cengiz has appealed to the US for help.
In an emotional article in the Washington Post, she wrote: “I implore President Trump and first lady Melania Trump to help shed light on Jamal’s disappearance.”
“We were in the middle of making wedding plans, life plans,” when he vanished, she said.
“Jamal is a valuable person, an exemplary thinker and a courageous man who has been fighting for his principles. I don’t know how I can keep living if he was abducted or killed in Turkey.”
Turkey says it will conduct a search of the Istanbul consulate.
Saudi Arabia’s foreign ministry said the country was “open to co-operation” and a search of the building could go ahead as part of the investigation.
Ankara is demanding that Saudi Arabia prove he left, while not providing definitive evidence to support the claim he was killed inside.
Who is Jamal Khashoggi?
A critic of Crown Prince Mohammed bin Salman, Mr Khashoggi was living in self-imposed exile in the US and writing opinion pieces for the Washington Post before his disappearance.
A former editor of the al-Watan newspaper and a short-lived Saudi TV news channel, he was for years seen as close to the Saudi royal family. He served as an adviser to senior Saudi officials.
But after several of his friends were arrested, his column was cancelled by the al-Hayat newspaper and he was allegedly warned to stop tweeting, Mr Khashoggi left Saudi Arabia for the US.