If Mr. Khashoggi was murdered inside the consulate, it will cast the Saudi regime and its de facto ruler, Crown Prince Mohammed bin Salman, in a new and disturbing light and require a thorough reevaluation of U.S. -Saudi relations.
Turkish investigators believe that Khashoggi, 59, was killed shortly after he entered and his body was later removed from the premises, a USA official and sources close to the investigation said.
The U.N. human rights office said Khashoggi's disappearance is "of serious concern".
Neil Quilliam, a senior research fellow for the Middle East and North Africa at the Chatham House think tank, said the Saudis were sure to notice when Trump said he knew "nothing" about Khashoggi's case. Those policies are all seen as initiatives of the crown prince, who has also presided over a roundup of activists and businessmen.
Khashoggi, a former Saudi government adviser, had been living in self-imposed exile in the United States since previous year fearing possible arrest.
Turkish President Recep Tayyip Erdogan has called for Saudi officials to prove their contention that Khashoggi left the consulate, as most accounts say the last he was seen was entering the building.
Khashoggi had entered the consulate to get documents for his forthcoming marriage. Erdogan has said he would await the results of an investigation.
"It points to the idea that whatever has happened to him, the Saudis-I mean, they've got some explaining to do", Corker told the Daily Beast. Rand Paul said he'd try to push through a Senate vote stalling US arms sales to Saudi Arabia.
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The capsule went into "ballistic descent mode" after the problem occurred, she said. It's the first space mission for Hague, who joined NASA's astronaut corps in 2013.
Officials also say they had become aware that Khashoggi may have been kidnapped before the second plane had departed, and monitored seven Saudis in a waiting room as they checked their luggage for a second time.
Turkish officials said Mr Khashoggi was killed on the premises and his body was then removed.
The journalist went to the building but "did not come back out", police were quoted as saying by Turkey's state-run Anadolu news agency.
Cengiz wrote in the op-ed that Khashoggi had gone to the Saudi consulate in Istanbul "despite being somewhat concerned that he could be in danger". While a military conflict is not likely to arise between Turkey and Saudi Arabia, this new development will place more strain on the relationship, further complicating the already hard situation in the Middle East.
Reacting to news of the alleged murder, the journalist's Turkish fiancee, Hatice Cengiz, said on Twitter she "did not believe he has been killed".
There he wrote opinion pieces for the Washington Post and continued to appear on Arab and Western TV channels.
The Turkish private NTV television said Ankara asked for permission for its investigators to search the consulate building, but a foreign ministry official would not confirm the report.
DailyMail.com said a friend of the journalist revealed that Mr Khashoggi's encrypted messages had been read after he vanished.
Saudi Arabia has always been a pillar of USA policy in the Middle East, and while the relationship was rocky during President Obama's tenure, Trump has embraced Riyadh. He was also a vocal critic of the Saudi Arabian government and fact that Riyadh has taken a harsh approach to members of the press who criticize the country's leadership lends some credence to the allegations of murder or imprisonment.