President Donald Trump in the Oval Office of the White House on October 23, 2018.

U.S. President Donald Trump said on Tuesday that Saudi authorities staged the "worst cover-up ever" in the killing of prominent journalist Jamal Khashoggi this month.

Asked by a reporter in the White House Oval Office how the Khashoggi killing could have happened, Trump said: "They had a very bad original concept. It was carried out poorly, and the cover-up was one of the worst in the history of cover-ups."

Khashoggi's death in the Saudi consulate in Istanbul on Oct. 2 has caused global outrage and strained relations between Riyadh and Washington. Khashoggi, a critic of Saudi Crown Prince Mohammed bin Salman, was a U.S. resident and columnist for The Washington Post.