Intelligence officials in the US have said Crown Prince Mohammed bin Salman gave the command for the murder of Mr Khashoggi in the Saudi consulate building in Istanbul, sources say.
And a Turkish newspaper now claims CIA director Gina Haspel has signalled to Turkish officials the agency has a secret recording of a call in which Prince Mohammed gave instructions to “silence” the Washington Post columnist.
According to Turkey’s Hurriyet newspaper, the call took place between Prince Mohammed and his brother, Saudi Arabia’s ambassador to Washington.
Hurriyet columnist Abdulkadir Selvi wrote: “It is being said that CIA chief Gina Haspel indicated this during her visit to Turkey.
“It is being said the crown prince gave orders to ‘silence Jamal Khashoggi as soon as possible’ in a call which was monitored by the US agency.”
Mr Khashoggi was killed six weeks ago in an operation Turkey’s President Tayyip Erdogan has said was ordered by the highest level of Saudi leadership.
After offering numerous contradictory explanations, Riyadh said last week Mr Khashoggi had been killed and his body dismembered when negotiations to persuade him to return to Saudi Arabia failed.
Saudi officials insist Prince Mohammed had no prior knowledge of Mr Khashoggi’s killing.
Reports of the new recording come just days after Donald Trump pledged his support for Prince Mohammed in a statement in which the President declared the US would remain a “steadfast partner” of the oil-rich kingdom despite the slaying.
Mr Trump said: “Our intelligence agencies continue to assess all information, but it could very well be that the Crown Prince had knowledge of this tragic event.
“Maybe he did and maybe he didn’t!”
Mr Trump has since faced calls from members of his own Republican party to review Washington’s links with Riyadh but Mr Trump insisted the benefits of a good relationship outweighed the possibility of Prince Mohammed’s involvement in the killing.
Saudi Arabia has warned criticism of the prince was a “red line”.
Foreign Minister Adel al-Jubeir said calls firm him to be held accountable for the killing “would not be tolerated”, nor would discussion of “anything disparaging”.