Turkish media outlets have published CCTV footage which they say shows evidence of a plot linked to missing Saudi journalist Jamal Khashoggi, BBC reports.
It shows men said to be Saudi intelligence officers entering and leaving Turkey via Istanbul airport.
Mr Khashoggi, a US resident and critic of the Saudi monarchy, entered the Saudi consulate in Istanbul on 2 October and has not been seen since.
Turkish authorities say Mr Khashoggi was killed. Saudi Arabia denies this.
On Wednesday US President Donald Trump condemned the disappearance. "We cannot let this happen to reporters, to anybody," he told reporters.
He said the situation was "serious" and wished to invite Mr Khashoggi's fiancée, Hatice Cengiz, to the White House.