One of the "hit squad" said to be involved in Jamal Khashoggi's death apparently changed into the journalist's clothes as part of a decoy attempt.
Broadcaster CNN says it has obtained footage which appears to show the man leaving the Istanbul consulate dressed in Mr Khashoggi's clothes and wearing glasses and a fake beard.
It was around 90 minutes after Mr Khashoggi had entered the building.
A senior Turkish official has identified the man as Mustafa al Madani and said he was later caught on camera wearing Ms Khashoggi's clothes at the city's famous Blue Mosque, according to CNN.
The source claims it suggests he was brought to the city to act as a body double and is reportedly of similar age and build to Mr Khashoggi.
CCTV from the consulate around two hours before the journalist arrived appears to show al Madani entering the building wearing different clothes.
Turkish officials say other images from later that afternoon show he had changed back into his original outfit and taken off the fake beard, CNN reports.
Another picture is said to show an alleged accomplice who was with al Madani throwing a bag in a large bin.
Officials reportedly believe the bag contained Mr Khashoggi's clothes and CNN says the footage is part of the ongoing investigation.
UK Prime Minister Theresa May said she condemned the killing of Mr Khashoggi "in the strongest possible terms", adding: "We must get to the truth of what happened."
Saudi Arabia has so far not responded to the latest claims.
It said earlier that its king and crown prince had called Mr Khashoggi's son to offer their condolences for his death.
The report by the state-run Saudi Press Agency said the journalist's son, Salah, had "expressed his sincere thanks" for the gesture.
Saudi Arabi has acknowledged that Mr Khashoggi - a fierce critic of Saudi rulers - died in the consulate.
However, its explanation that the 59-year-old was unintentionally killed in a "fist fight" was met with international scepticism.
In the latest comments by the kingdom, the Saudi foreign minister Adel al Jubeir insisted his country did not know how the journalist was killed or where his body was.
He described Mr Khashoggi's death as an "aberration, a mistake" that Crown Prince Mohammed bin Salman was not aware of.
Mr al Jubeir told Fox News: "This was an operation that was a rogue operation.
"This was an operation where individuals ended up exceeding the authorities and responsibilities they had.
"They made the mistake when they killed Jamal Khashoggi in the consulate and they tried to cover up for it," he said.
Saudi Arabia's admission that he had died in the consulate came after several weeks of insisting he had walked out alive on 2 October - the day he was reported missing.
Turkish officials have given a very different narrative to the Saudis.
They have told the media he was brutally tortured and killed in a premeditated murder by a 15-man "hit squad" that flew in by private jet.
They also claim to have audio evidence of the murder.
On Tuesday, Turkish media also reported that a car belonging to the Saudi consulate had been found in the Sultangazi district of the city.
The country's president, Recep Tayyip Erdogan, has said he will soon reveal details of how Mr Khashoggi died.
Mr Erdogan promised to explain all the details of the case in a speech to his party on Tuesday.
"We are looking for justice here and this will be revealed in all its naked truth, not through some ordinary steps but in all its naked truth," Mr Erdogan told a rally in Istanbul.
His comments were backed up by US President Donald Trump, who also said he expected what happened to come out by then, adding he would speak to Saudi Crown Prince Mohammed bin Salman "very soon".
In an interview with The Washington Post at the weekend, Mr Trump appeared more critical of the Saudis, saying "obviously there's been deception, and there's been lies".
The UK, France and Germany have issued a joint statement condemning the killing "in the strongest possible terms", saying there "remains an urgent need for clarification of exactly what happened".
German Chancellor Angela Merkel has also suspended arms sales to Saudi Arabia.
Meanwhile, Mr Khashoggi's fiancee - who is a Turkish national - is under 24-hour police protection, the Istanbul governor's office told Sky News.
Hatice Cengiz waited for hours outside the Saudi consulate before alerting authorities - as he had asked her to if he did not re-emerge.
Mr Khashoggi had entered the consulate to get papers so they could get married.
The search for his body is continuing, with a large forest near Istanbul the focus of the search.
Saudi officials said on Friday that they had arrested 18 people and fired their deputy intelligence chief and royal court adviser.
However, critics have claimed it is an effort to shield the country's crown prince, who they say would almost certainly have had knowledge of the plan.
A leading US Republican senator said he believed the crown prince was behind the killing and said Saudi explanations had lost credibility.
"Yes, I think he did it," Bob Corker, chairman of the senate foreign relations committee, told CNN.
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