The order to kill journalist Jamal Khashoggi came from the "highest levels" of the Saudi government, Turkish President Tayyip Erdogan said in an op-ed piece published by the Washington Post, ABC News reported.

However, he wrote: "I do not believe for a second that King Salman, the custodian of the holy mosques, ordered the hit on Khashoggi."

He said that despite a longstanding relationship between Turkey and Saudi Arabia, Istanbul would not "turn a blind eye to the premeditated murder that unfolded in front of our very eyes".

"The killing of Khashoggi is inexplicable," he wrote.

"Had this atrocity taken place in the United States or elsewhere, authorities in those countries would have gotten to the bottom of what happened."