The US government has asked Turkey to hand over a tape which is said to prove that missing journalist Jamal Khashoggi was killed inside the Saudi consulate in Istanbul.

Turkish officials said the recording contains horrific evidence of the Saudi journalist’s death.

President Donald Trump told reporters on Wednesday: “We have asked for it, if it exists”, adding that it “probably” does exist.

US Secretary of State Mike Pompeo has been in Saudi Arabia and Turkey this week, with the President saying the truth will emerge by the end of the week.

Trump has previously said “rogue killers” were responsible for Khashoggi’s suspected murder, as he denied that he was providing cover for Saudi Arabia.

It is claimed that Saudi consul Mohammed al-Otaibi was heard in the audio recording telling Saudi agents to “do this outside. You’re going to get me in trouble”.

Khashoggi has not been seen since he entered the Saudi consulate in Turkey on the afternoon of October 2. He was due to collect documents which would allow him to marry his fiancé, Hatice Cengiz, who waited for him outside.

Amid growing international outrage, the Washington Post published Khashoggi’s final column, which he wrote before his disappearance.

The piece, titled “What the Arab world needs most is free expression”, was submitted to the newspaper’s global opinion editor, Karen Attiah, the day after Khashoggi vanished.

In it, he wrote spoke of the importance of a free press and wrote: “The Arab world is facing its own version of an Iron Curtain, imposed not by external actors but through domestic forces vying for power”.

Attiah said she held off from publishing the piece in hopes that “he would come back to us so that he and I could edit it together.”

She added: “Now I have to accept: That is not going to happen.

“This column perfectly captures his commitment and passion for freedom in the Arab world. A freedom he apparently gave his life for.”

Meanwhile, it has emerged that one of the men alleged to be involved in Khashoggi’s disappearance and death was a high-ranking, Sandhurst-trained officer.

Described as a right-hand man of Crown Prince Mohammad bin Salman, broadcaster CNN cited sources who said he was linked to the Saudi royal and deputy Prime Minister.

Another man under investigation by Turkish authorities is Maher Abdulaziz Mutreb, a Saudi intelligence officer said to be close to bin Salman, according to CNN.

It follows a search of the Saudi consulate in Turkey, as well as the consul’s home earlier this week.

Turkish officials believe 15 Saudi men who arrived in Istanbul on the day of Khashoggi’s disappearance are responsible for his death.

Saudi Arabia has denied killing Khashoggi.