Khashoggi was a frequent contributor to the Washington Post and other western publications.
A friend of a prominent Saudi journalist who went missing in Istanbul said Sunday that officials told him to "make your funeral preparations" as the Washington Post contributor "was killed" at the Saudi Consulate. His fiancee, waiting outside, said he never emerged and Turkish sources said they believe Khashoggi, a prominent critic of Saudi policies, was killed inside the mission. Salman said Turkish officials were welcome to search the building, insisting, "We have nothing to hide".
"The initial assessment of the Turkish police is that Mr. Khashoggi has been killed at the consulate of Saudi Arabia in Istanbul".
The European Union fully supports U.S. Secretary of State Mike Pompeo, who called on Riyadh to investigate Khashoggi's disappearance, EU policy chief Federica Mogherini said.
Trump has repeatedly lashed out at the media, calling it the "enemy of the people", and has raised human rights prominently only when pressuring U.S. antagonists such as Iran and China.
On Monday President Trump said that he was "concerned" about reports on Khashoggi's disappearance. It has allowed journalists into the consulate to show Mr Khashoggi is not there, reportedly even opening cupboards.
"Diplomats get absolute immunity from criminal prosecutions, so if an ambassador was involved in the murder, they can't be touched", Professor Saul said.
Khashoggi, a critic of Saudi Crown Prince Mohammed bin Salman and Saudi Arabia's intervention in Yemen, has been living in exile in the United States to avoid arrest.
Turkish authorities are set to search the site after announcing that Saudi Arabia had declared itself "open to co-operation" in the investigation, but no date has been announced for the search.
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Investigators said a 15-person team arrived at the consulate on Tuesday, returning to Riyadh the same day.
Saudi Arabia is a longtime ally of the United States, but on Monday senior US officials expressed alarm over Khashoggi's disappearance.
"The request that America made to Saudi Arabia and other OPEC countries is to be sure that if there is any loss of supply from Iran, that we will supply that". He left the country previous year for the United States fearing retribution from the kingdom which has recently witnessed widespread crackdown on dissent. A former Muslim Brotherhood member who befriended Osama bin Laden but later condemned his violence, Khashoggi became a leading proponent for Arab reform-some of the same reforms, in fact, that MBS has spearheaded as part of his Vision 2030 campaign for the kingdom.
'Despite that, we have seen over the last few days various malicious leaks and grim rumors flying around about Jamal's whereabouts and fate, ' the statement says. "Jamal was - or, as we hope, is - a committed, courageous journalist".
European Union policy chief Federica Mogherini expressed support for Pompeo's statement on Tuesday and said the EU is "fully aligned with the USA position on this".
"Do you not have cameras and everything of the sort?"
Republican Senator Lindsey Graham said Riyadh must provide "honest answers" about the journalist.
The foreign secretary, Jeremy Hunt, has warned Saudi Arabia that its friendship with the United Kingdom depends on shared values, after he demanded answers over claims that a Saudi hit squad may have played a role in the disappearance and possible killing of Jamal Khashoggi. But if by some miracle Khashoggi is still alive in a Saudi prison somewhere, revealing that he spoke anonymously to a foreign reporter could have enraged his captors and jeopardized his life.