Turkish authorities are investigating the disappearance of a veteran Saudi journalist, according to the country’s official news agency.

Ruling party spokesman Omer Celik said authorities will find out what happened to “lost journalist” Jamal Khashoggi and who was responsible for his disappearance.

“A journalist disappearing like this in a secure country like the Republic of Turkey is something that will be followed up with sensitivity,” Mr Celik said, as quoted by the Anadolu news agency.

Anadolu said the Istanbul public prosecutor’s office began a probe into Mr Khashoggi’s disappearance on Tuesday, immediately after he went missing.

It said the investigation over allegations that the writer was detained had “deepened”.

Mr Khashoggi, 59, went missing while on a visit to the consulate in Istanbul for paperwork to marry his Turkish fiancee.

The consulate insists the writer left its premises, contradicting Turkish officials who say they believe he is still there.

The agency, citing police, said Mr Khashoggi did not leave the building adding that 15 Saudi officials, on two planes, had arrived in Istanbul and were at the consulate around the same time.

It said the officials returned to Saudi Arabia.

Mr Khashoggi has written columns for the Washington Post critical of Saudi Arabia’s assertive Crown Prince Mohammed bin Salman.