Washington, Oct 19 (IANS): Saudi intelligence officer and former diplomat Maher Abdulaziz Mutreb played a "pivotal role" in the apparent assassination of Saudi journalist Jamal Khashoggi, a source familiar with the Turkish investigation told CNN.

The source said on Thursday that Mutreb was fully aware of "the plot" of the operation.

Mutreb, who was the first secretary at the Saudi embassy in London and has been described as a colonel in Saudi intelligence, is closely connected to Saudi Crown Prince Mohammed bin Salman.

"He was seconded to an elite protection brigade within the Royal Guard to serve as the personal security force of (the Crown Prince)," the source told CNN.

Mutreb appeared in photographs alongside the Crown Prince during his tour of the US earlier this year.

US officials told CNN that any operation involving members of the Crown Prince's inner circle could not have happened without his direct knowledge.

Security camera images that purport to show the movements of Mutreb, one of 15 Saudi men believed by Turkish authorities to be connected to the disappearance and apparent death of Khashoggi, were published on Thursday by a Turkish newspaper.

Turkish investigators continue to hunt for clues to what happened to Khashoggi amid growing indications that some of the men allegedly responsible for the journalist's killing have close ties to the highest levels of the Saudi government.

The four images, which pro-government paper Sabah said it obtained from Turkish security sources, purportedly show Mutreb in Istanbul on October 2,.

Khashoggi, a Washington Post columnist, visited the Saudi consulate in Istanbul on October 2 to obtain papers that would have allowed him to marry his Turkish fiancee.

The insider-turned-critic of the Saudi government has not been seen since.