'Rogue killers - who knows?': Donald Trump discusses mystery of missing journalist with Saudi Arabia’s King Salman

President Donald Trump has spoken to King Salman of Saudi Arabia about missing Saudi journalist, Jamal Khashoggi, who visited the Saudi Consulate in Istanbul and is feared dead.

"I just spoke with the King of Saudi Arabia who denies any knowledge to the Saudi Arabian citizen", Mr Trump said to reporters on Monday.

"I have asked Secretary of State Mike Pompeo to get on a plane and go to Saudi Arabia... go to Turkey if necessary."

When pushed on what King Salman thinks happened, Mr Trump said: "He didn't really know. Maybe I don't want to get into his mind, but it sounded to me like maybe these could have been rogue killers - who knows?

"We are going to try to get to the bottom of this very soon. But, his was a flat denial."

Jamal Khashoggi has not been seen since October 2. Credit: AP

Khashoggi's disappearance almost two weeks ago has sparked an international uproar involving the kingdom, Turkey and the United States that remains unresolved.

Mr Khashoggi - a Washington Post contributor - had written columns critical of Saudi Crown Prince Mohammed bin Salman, the kingdom’s war in Yemen and its crackdown on activists and businessmen.

Turkish officials say they fear a team of Saudi agents killed and dismembered Mr Khashoggi, and they have released surveillance footage of the alleged perpetrators and mysterious movements outside the consulate on October 2, the day he entered.

The kingdom says the allegations are “baseless” but has offered no evidence Mr Khashoggi ever left the consulate.