Saudi Arabia has granted permission for Turkish investigators to search the kingdom’s Istanbul consulate, a senior Turkish official said on Tuesday amid mounting pressure on Riyadh over the disappearance of a missing journalist.

Hami Aksoy, a spokesman for the Turkish ministry of foreign affairs, said in a written statement that Saudi authorities have told Ankara that they will co-operate with the probe into the fate of Jamal Khashoggi, a prominent commentator who vanished after visiting the diplomatic mission. “The Saudi authorities have said that they are open to co-operation and that a search of the consulate building can be conducted,” he said. “A search of the consulate building will be conducted within the framework of the investigation.”

Riyadh has faced growing calls to help explain the disappearance of Mr Khashoggi, a veteran commentator with 1.6m Twitter followers and a regular column in the Washington Post. The journalist, who went into self-imposed exile in the US last year, visited the consulate building last Tuesday to collect documents for his forthcoming marriage. He had been due to meet his fiancée, who was waiting outside, after attending the appointment but she said that he failed to turn up.

Turkish officials and friends of Mr Khashoggi have suggested that he was murdered. That has been strongly rejected by Saudi Arabia, which has insisted that he left the building.

Riyadh has faced growing pressure to co-operate in the investigation, including from the US, the Gulf kingdom’s most important international ally. On Monday, Donald Trump and his vice-president Mike Pence voiced concern about the missing commentator. Mike Pompeo, the US secretary of state, urged Riyadh to “support a thorough investigation of Mr Khashoggi’s disappearance and to be transparent about the results of that investigation.”

The Washington Post on Tuesday published an image from CCTV that it said showed Mr Khashoggi entering the Istanbul consulate. Recep Tayyip Erdogan, the Turkish president, has urged Saudi Arabia to prove that he came out alive.