Bruce Riedel, a former C.I.A. analyst who advised four presidents and is now at the Brookings Institution, called Khashoggi's disappearance consistent with the pattern of "crude intimidation" and the growing silencing of dissent in Saudi Arabia.
The Saudis have offered no surveillance footage or evidence to corroborate their claims that Khashoggi left the consulate, and Turkish authorities have not provided evidence to show why they believe the columnist was killed there.
U.S. President Donald Trump speaks to reporters as he returns from Florida, on the South Lawn of the White House in Washington, U.S. October 8, 2018.
"See when I hear arrest of a friend who did nothing that is worth to be arrested, make me feel I shouldn't go".
On Monday, Downing Street said the United Kingdom was "working urgently" to establish the facts behind Mr Khashoggi's disappearance.
"I'm not sure. We are investigating this through the foreign ministry to see exactly what happened at that time", he added.
The planes belonged to a company based in Saudi Arabia which has links to the state.
He visited the consulate in Istanbul on October 2 to obtain documentation to finalize his divorce; his Turkish fiancée waited for him outside the building, and reported him missing after he didn't return.
"Jamal is a Saudi citizen whose safety and security is a top priority for the Kingdom, just as is the case with any other citizen", read an email from Saudi Crown Prince Mohammed bin Salman that he sent to close contacts and was obtained by Fox News on Monday.
Turkish Foreign Ministry said on Tuesday that an examination will be carried out in the Saudi consulate in Istanbul and that Saudi authorities were open to cooperation. I don't know who is behind these claims, or their intentions, nor do I care frankly. She accused Saudi Arabia of "state terrorism" and called on the global community to take action against the kingdom.
Relations between Turkey and Saudi Arabia - already under severe strain - have taken more beating after leading Saudi journalist, Jamal Khashoggi's death, who is suspected to have been murdered inside the Saudi Consulate in Istanbul.
Saudis are, perhaps, trying to flawless their excellence in furtherance of their plans and the world must expect more covert operations by Saudi Arabia in a not-so-distant future with Iran as its primary target.
Turkish investigators have hinted they know more about the disappearance than they have disclosed.
"When President Trump became president, we've changed our armament strategy again for the next 10 years to put more than 60% with the United States of America", he added.
In November, dozens of princes, businessmen and senior officials were detained in what the authorities said was an anti-corruption crackdown.
Saudi Crown Prince Mohammed bin Salman said last week that Riyadh was "ready to welcome the Turkish government to go and search our premises", because it had "nothing to hide" about the missing journalist, 59-year-old Jamal Khashoggi.