Saudi Arabia is preparing a report that would admit Saudi journalist Jamal Khashoggi was killed as the result of an interrogation that went wrong, CNN reported on Monday, citing two unnamed sources.

One source cautioned that the report was still being prepared and could change, CNN said. The other source said the report would likely conclude that the operation was carried out without clearance and that those involved will be held responsible, the cable news outlet said.

Turkish police investigators entered Saudi Arabia's Istanbul consulate on Monday, two weeks after the disappearance of the journalist.

Turkish authorities have an audio recording which indicates that he was killed in the Saudi consulate in Istanbul, a Turkish official and a security source said on Monday.

"Turkish police have an audio recording that indicates that Khashoggi was killed in the Saudi consulate", the security source told Reuters. He gave no further details.

Saudi Arabia has strongly denied killing Khashoggi, a critic of the kingdom's policies. Its interior minister has described the assertion as "lies". Saudi officials have said he left the consulate shortly after entering it.

Khashoggi, a Washington Post columnist and US resident, has not been seen since entering the consulate on October 2 to obtain documents for his forthcoming marriage. His fiancée said he never left the building.