Erdogan said he himself was following the investigation, saying it was his political and humanitarian duty. He said police were examining CCTV footage of entrances and exits at the consulate and Istanbul airport.
Both planes' final destination was the Saudi capital of Riyadh. The ambassador declined to discuss the matter further, saying, "We don't want to harm the investigation".
"I have raised Jamal's disappearance personally with the Saudi ambassador, and while we await more information, know we will respond accordingly to any state that targets journalists overseas", he wrote.
This reaction, as well as the circulation over Twitter of news stories about the murders of a Kuwaiti businessman and the leader of an Iranian opposition television channel, aim to portray Turkey as a lawless, Islamist-led country - and Khashoggi's disappearance as a effect of that environment, rather than part of a Saudi plot.
Saudi officials said hours after Khashoggi's disappearance that he had left the diplomatic mission.
The Khashoggi case puts the Trump administration unexpectedly on the side of Turkey, where two top government officials have been slapped with USA sanctions over the detention of an American pastor. But she says she never saw him re-emerge.
Saudi officials have denied allegations that Khashoggi was killed at the consulate, calling them "baseless".
Still, the Trump administration last month stood behind its support for that campaign with weapons, logistics and intelligence, certifying that the Saudis were taking adequate steps to prevent civilian deaths despite mounting evidence to the contrary.
But analysts said Khashoggi might have been considered especially risky by the Saudi leadership because he was not a longtime dissident, but rather a pillar of the Saudi establishment who was close to its ruling circles for decades, had worked as an editor at Saudi news outlets and had been an adviser to a former Saudi intelligence chief.
In his first comments over the disappearance, Turkish President Recep Tayyip Erdogan on Sunday said he was awaiting the results of an investigation. Following the initial announcement by Turkish sources of Khashoggi's killing, she tweeted in Arabic her refusal to believe that is the case. "Because if he was alive, Saudis would provide evidence that he is alive", Aktay told CNN during a telephone interview in Istanbul.
Turkish officials have said they believe Saudi writer and government critic Jamal Khashoggi, was killed inside the consulate after he visited the mission to obtain a document required to marry his Turkish fiancee.
U.S. President Donald Trump said on Tuesday he plans to speak with the Saudis without elaborating.
Mr Kislakci also alleged, based on conversations with officials, that Mr Khashoggi was made to "faint", before being dismembered.
U.S. officials have stated that they are following this case closely.
On Sunday, Erdogan did not directly repeat the investigators' fears about Khashoggi being dead when talking to reporters following a meeting of his Justice and Development Party in Ankara, Turkey's capital.
The fiancée reportedly went with him, but had to wait outside, and Khashoggi failed to return. Their ambassador to the USA insists that he personally had a friendly relationship with Khashoggi and remained in contact whenever both of them were in Washington.
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