FEARS are growing for the safety of a top journalist following shock claims he has been murdered and dismembered INSIDE a Saudi consulate.

Jamal Khashoggi's colleagues at the Washington Post say if the reports from Turkish officials turn out to be true it would be a "monstrous and unfathomable act".

4 Jamal Khashoggi has not been seen since visiting the Saudi consulate in Istanbul Credit: EPA

The Saudi national has not been seen since visiting his hardline country's consulate in Istanbul with his girlfriend on Tuesday.

An anonymous Turkish official has told told the BBC there are worrying signs he was murdered while there.

But Saudi Arabia has strongly denied the accusations and insists it is "working to search for him" and has nothing to hide.

Turan Kislakci, a friend of Khashoggi and the head of the Turkish-Arab Media Association, told AP that Turkish officials said the journalist has been brutally murdered.

4 Turkish officials have opened a full investigation into the murder claims Credit: AFP or licensors

4 Khashoggi's Turkish fiancee Hatice waits in front of the Saudi Arabian consulate Credit: AFP or licensors

"What was explained to us is this: 'He was killed, make your funeral preparations'," Mr Kislakci said.

Mr Kislakci also claimed, based on conversations with anonymous officials, that Khashoggi was made to "faint", and was then dismembered.

Turkish officials have opened full investigation into the claims.

"The initial assessment of the Turkish police is that Mr Khashoggi has been killed at the consulate of Saudi Arabia in Istanbul," Turkish officials told Reuters.

"We believe that the murder was premeditated and the body was subsequently moved out of the consulate."

They said a team of 15 Saudi officials were sent to Turkey to kill the 59-year-old on the day he vanished.

It is understood they knew ahead of time that he would be visiting the consulate that day - having visited last week and been asked to return on Tuesday.

They have not given any evidence for the claims or given any hints to how he might have been killed.

4 Saudi Crown Prince Mohammed bin Salman said his country has nothing to hide Credit: Getty - Contributor

"If the reports of Jamal's murder are true, it is a monstrous and unfathomable act," Fred Hiatt, the Washington Post's editorial page editor, said in a statement.

"Jamal was - or, as we hope, is - a committed, courageous journalist. He writes out of a sense of love for his country and deep faith in human dignity and freedom."

On Tuesday, he went to the consulate to obtain a document certifying he had divorced his ex-wife, so that he could marry his Turkish fiancée, Hatice Cengiz.

She said she waited outside for 11 hours, but he did not come out.

Khashoggi is a high-profile critic of Saudi Arabia and its Crown Prince Mohammed bin Salman - and has more than 1.6 million Twitter followers.

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Prince Mohammed bin Salman has said the Turkish authorities are welcome to search the building because "we have nothing to hide".

The prince said: "He's a Saudi citizen and we are very keen to know what happened to him. And we will continue our dialogue with the Turkish government to see what happened to Jamal there.

"My understanding is he entered and he got out after a few minutes or one hour. I'm not sure. We are investigating this through the foreign ministry to see exactly what happened at that time."