A man appearing to wear Jamal Khashoggi's clothes can be seen on surveillance video leaving the Saudi consulate in Istanbul after the journalist was killed there, according to newly leaked surveillance footage.

The footage appeared after it emerged a member of Saudi Crown Prince Mohammed bin Salman's entourage made four calls to his office from the consulate the day Khashoggi disappeared, a Turkish newspaper reported.

EXCLUSIVE: Surveillance footage shows Saudi operative in Jamal Khashoggi's clothes in Istanbul after the journalist was killed, Turkish source says https://t.co/6GdiyKOeYB pic.twitter.com/6IefJb6GJe — CNN (@CNN) October 22, 2018

The claim on Monday comes a day before Prince Mohammed's high-profile investment summit begins in Riyadh.

Turkish president Recep Tayyip Erdogan has promised to detail Khashoggi's killing "in all its nakedness", raising international pressure on Saudi Arabia.

Meanwhile, Turkish crime scene investigators have arrived at an underground car park in Istanbul where authorities earlier found a vehicle belonging to the Saudi consulate.

Saudi Arabia's claim that Khashoggi died in a "fistfight" was met with international scepticism and allegations of a cover-up in order to absolve the 33-year-old crown prince of direct responsibility.

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Turkish media reports and officials maintain that a 15-member Saudi team flew to Istanbul on October 2, knowing Khashoggi would arrive to pick up a document he needed in order to get married.

Once he was inside the diplomatic mission, reports claimed the Saudis accosted 59-year-old Khashoggi, cut off his fingers, then killed and dismembered him.

CNN aired surveillance footage showing a man in Khashoggi's dress shirt, suit jacket and trousers.

It cited a Turkish official as describing the man as a "body double" and a member of the Saudi team sent to Istanbul to target the writer.

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The man is seen in the footage walking out of the consulate via its back exit with an accomplice, then taking a taxi to Istanbul's famed Sultan Ahmed Mosque, where he went into a public toilet, changed back out of the clothes and left.

A report in Yeni Safak said Maher Abdulaziz Mutreb, a member of Prince Mohammed's entourage on trips to the United States, France and Spain this year, made fours calls from the consulate.

The newspaper said the four calls went to Bader al-Asaker, the head of Prince Mohammed's office. It said another call went to the United States.

Meanwhile, Saudi state media reported that both Prince Mohammed and King Salman made calls to Khashoggi's son Salah early on Monday morning.

Statements from the agency said both the king and the crown prince expressed their condolences over Khashoggi's death.

Five Turkish employees of the Saudi consulate have also given testimonies to prosecutors, Turkish media reported.

Istanbul's chief prosecutor had summoned 28 more staff members of the Saudi consulate, including Turkish citizens and foreign nationals, to give evidence.

Some Turkish employees reportedly said they were instructed not to go to work around the time Khashoggi disappeared.

Saudi foreign minister Adel al-Jubeir told Fox News that Khashoggi's killing was "a rogue operation" and that "we don't know where the body is".