Billionaire businessman Sir Richard Branson has ratcheted up pressure on Saudi Arabia over the disappearance of a prominent journalist by freezing several business links to the Gulf kingdom. The Virgin Group founder joined a mounting chorus of international concern about the fate of Jamal Khashoggi, who vanished last week. The journalist has not been seen since visiting the Saudi consulate in the Turkish city of Istanbul, sparking claims he was killed in the building. Foreign Secretary Jeremy Hunt and US President Donald Trump are among the political figures who have demanded answers from Saudi Arabia over the case. On Thursday evening, Sir Richard said he would be suspending his directorship of two tourism projects in the country, while Virgin would halt discussions with the Saudis over investment in its space projects. Sir Richard Branson Credit: James D. Morgan/Getty He warned that, if fears are confirmed, the West would struggle to continue doing business with the Gulf kingdom. His statement said: "I had high hopes for the current government in the Kingdom of Saudi Arabia and its leader Crown Prince Mohammed bin Salman and it is why I was delighted to accept two directorships in the tourism projects around the Red Sea. "I felt that I could give practical development advice and also help protect the precious environment around the coastline and islands. "What has reportedly happened in Turkey around the disappearance of journalist Jamal Khashoggi, if proved true, would clearly change the ability of any of us in the West to do business with the Saudi Government. "We have asked for more information from the authorities in Saudi and to clarify their position in relation to Mr Khashoggi. "While those investigations are ongoing and Mr Khashoggi's presence is not known, I will suspend my directorships of the two tourism projects. Virgin will also suspend its discussions with the Public Investment Fund over the proposed investment in our space companies Virgin Galactic and Virgin Orbit." Police CCTV allegedly shows suspects in the case of missing Saudi journalist Jamal Khashoggi Credit: AFP His interventions comes after a Turkish newspaper published the names and photographs of 15 Saudi nationals who allegedly arrived in Istanbul on two private jets the day Mr Khashoggi went missing. The Sabah newspaper, which is close to Turkish president Recep Tayyip Erdogan, revealed the identities of what it called a "mysterious" 15-member "assassination squad" who were allegedly involved in the disappearance. A critic of the kingdom's de facto ruler Crown Prince Mohammed bin Salman, Mr Khashoggi was living in self-imposed exile in the US and writing opinion pieces for the Washington Post before he vanished. He visited the consulate last Tuesday to obtain a document confirming he had divorced his ex-wife, in order to allow him to remarry. Turkish officials have said he was killed on the premises and his body removed. On Tuesday, Jeremy Hunt met the Saudi ambassador and spoke by telephone to his counterpart in the state to voice the UK's concerns about the case. Mr Hunt said that if reports of Mr Khashoggi's death proved correct, the UK would regard the situation as "serious", adding: "Friendships depend on shared values." Mr Hunt urged the Saudi Government to co-operate fully with the Turkish investigation into the case, and to provide further information as soon as possible. The Turkish authorities are set to conduct a search of the Istanbul consulate building after announcing that Saudi Arabia had declared itself "open to co-operation" in the investigation. Turkish President Recep Tayyip Erdogan has not confirmed the alleged killing, saying he would await the result of an investigation. Saudi officials have denied the allegations as baseless.