Saudi Crown Prince Mohammed bin Salman has called the son of Jamal Khashoggi to express condolences, the kingdom has announced.

The journalist was killed at the Saudi Consulate in Istanbul, Turkey, by officials that allegedly included a member of the royal’s entourage.

King Salman similarly made a condolence call as international pressure on the kingdom continues to rise, even after it acknowledged on Saturday that the Washington Post journalist was killed on October 2 at the consulate under still-disputed circumstances.

Jamal Khashoggi
The circumstances around Jamal Khashoggi’s death are still unconfirmed (AP Photo/Hasan Jamali, File)

Turkish President Recep Tayyip Erdogan has said that he will “go into detail” about the Khashoggi case in a speech in parliament on Tuesday, the same day a glitzy investment forum in Riyadh spearheaded by Prince Mohammed is to take place.

Saudi Arabia’s explanation that Mr Khashoggi was killed in a “fistfight” and 18 Saudis have been detained has been met with international scepticism and allegations of a cover-up designed to absolve Prince Mohammed of direct responsibility.

Turkish media reports and officials say a 15-member Saudi team flew to Istanbul, laid in wait for Mr Khashoggi at the consulate and then cut off his fingers, killed and dismembered the 59-year-old writer.

“Why did these 15 people come here? Why were 18 people arrested? All of this needs to be explained in all its details,” Mr Erdogan said.

Turkish President Recep Tayyip Erdogan
Turkish President Recep Tayyip Erdogan says he will go into detail about the Khashoggi case in a speech in parliament on Tuesday (Presidential Press Service via AP, Pool)

The state-run Saudi Press Agency announced the calls to Mr Khashoggi’s son, Salah, early on Monday morning. Statements from the agency said both King Salman and Prince Mohammed express their condolences for his father’s death.

The call comes after a leaked photograph apparently taken from surveillance footage shows Maher Abdulaziz Mutreb, a member of Prince Mohammed’s entourage on trips to the United States, France and Spain this year, at the consulate, just ahead of Mr Khashoggi’s arrival.

Mutreb’s name also matches that of a first secretary who once served as a diplomat at the Saudi Embassy in London, according to a 2007 list compiled by the British Foreign Office.

Saudi Arabia so far has not acknowledged or explained Mutreb’s presence in Istanbul — nor that of a forensics and post-mortem expert, also on hand for Mr Khashoggi’s arrival at the consulate.

Istanbul’s chief prosecutor summoned 28 more staff members of the Saudi Consulate, including Turkish citizens and foreign nationals, to give evidence on Monday, Turkish state broadcaster TRT reported.

Prosecutors have previously questioned consulate staff; some Turkish employees reportedly said they were instructed not to go to work around the time that Mr Khashoggi disappeared.

Turkish news agency Anadolu Agency reported on Sunday that Mr Khashoggi’s fiancee, Hatice Cengiz, has been given 24-hour police protection.

Also on Sunday, images that were obtained by TRT World, a Turkish news channel that broadcasts in English, showed Mr Khashoggi as he arrived at a police barrier before entering the consulate on October 2. The images, taken from security camera video, show the writer being searched before continuing towards the building.