The TV channel said it obtained exclusive law enforcement surveillance footage, part of the Turkish government's investigation, that appeared to show the man leaving the Saudi consulate by the back door, wearing Khashoggi's clothes, a fake beard and glasses.

The Turkish official identified the man in the video as Mustafa al-Madani, who was allegedly part of what investigators said was a hit squad, sent to kill the journalist at the Saudi consulate during an appointment on October 2 to get papers for his upcoming wedding.

The same man was seen in Khashoggi's clothing, according to the Turkish case, at the city's famous Blue Mosque hours after the journalist was last seen alive entering the consulate.

After weeks of denying involvement in Khashoggi's disappearance, Saudi Arabia has given a shifting narrative of what happened to the journalist.

The Kingdom admitted last week that Khashoggi, a critic of Crown Prince Mohammed bin Salman's policies, was killed in the Istanbul consulate, saying his death was the result of a "fistfight".

Later, a Saudi source close to the royal palace told CNN that the Washington Post journalist died in a chokehold.

On Sunday, Saudi Arabia's Foreign Minister Adel al-Jubeir described Khashoggi's death on Fox News as a "murder" and a "tremendous mistake".

According to the Turkish official, Madani, 57, of similar height, age and build to Khashoggi, 59, was used as a decoy for the journalist.

Another senior Turkish official told CNN that the video showed that Madani was brought to Istanbul to act as a body double.

"You don't need a body double for a rendition or an interrogation," the official said. "Our assessment has not changed since October 6. This was a premeditated murder and the body was moved out of the consulate."

US President Donald Trump said there had been "deception" and "lies" in Saudi Arabia's explanation, having previously said he found their narrative to be "credible".

The UK, France and Germany issued a joint statement expressing shock at the death and demanding a full explanation, saying: "Nothing can justify this killing and we condemn it in the strongest possible terms."

Meanwhile, Turkish President Recep Tayyip Erdogan said he would reveal the "naked truth" of the matter in Parliament on Tuesday.

Turkey has so far stopped short of officially blaming Saudi Arabia for the killing, though its investigators say they have audio and video evidence which shows Khashoggi was killed by a team of Saudi agents inside the consulate.