U.S. President Donald Trump said on Monday "rogue killers" may have been behind the disappearance of prominent Saudi journalist Jamal Khashoggi and dispatched Secretary of State Mike Pompeo to meet King Salman over the case.

Khashoggi, a U.S. resident, Washington Post columnist and leading critic of the powerful Saudi crown prince, Mohammed bin Salman, vanished after entering the Saudi consulate in Istanbul two weeks ago to get marriage documents. Turkish officials say they believe he was murdered there and his body removed, in a case that has provoked an international outcry.

Turkish authorities have an audio recording indicating that Khashoggi was killed in the consulate, a Turkish official and a security source told Reuters, and have shared evidence with countries including Saudi Arabia and the United States. They provided no further details.