Turkish authorities believe that journalist and Saudi Arabia critic Jamal Khashoggi, who disappeared in Turkey last week, was killed at the Saudi Consulate in Istanbul, a senior Turkish official and another regional diplomat told NBC News.

The Washington Post, which published Khashoggi’s work, reported Saturday that Turkey believed he was killed by a Saudi kill team, citing two people with knowledge of the investigation.

Khashoggi, a Saudi journalist who writes an opinion column for The Washington Post, disappeared last week after entering the Saudi consulate in Turkey’s largest city and hasn’t been seen since. Saudi Arabia’s government has said Khashoggi left the consulate building and that they’re looking into what happened to him afterward, while Turkey had said previously it believed Khashoggi was still in the consulate.

“The initial assessment of the Turkish police is that Mr. Khashoggi has been killed at the consulate of Saudi Arabia in Istanbul,” the Turkish official told NBC News on Saturday. “We believe that the murder was premeditated and the body was subsequently moved out of the consulate.”

The Washington Post, in a statement from editorial page editor Fred Hiatt, said the newspaper has been “enormously proud to publish his writings” and called Khashoggi a “committed, courageous journalist.”

"If the reports of Jamal's murder are true, it is a monstrous and unfathomable act,” Hiatt said.

In a statement released late Saturday, the Saudi Consulate in Istanbul denied the reports from Turkish officials, calling them "baseless allegations." The statement said a Saudi security delegation arrived in Instanbul on Saturday to help authorities investigate Khashoggi's disappearance. Khashoggi is a Saudi citizen.

The Committee to Protect Journalists on Saturday called on Saudi Arabia to account for Khashoggi's whereabouts.