On Tuesday last week, Jamal Khashoggi walked into the Saudi consulate in Istanbul for a scheduled appointment. He has not been heard from since. Khashoggi, perhaps the most high-profile Saudi critic of crown prince Mohammed bin Salman, had reportedly weighed up the risks of visiting the consulate, where officials had agreed to provide him with documents he needed to initiate his marriage to his fiancée in Turkey. “He said, ‘the most they can do is interrogate me. And I can give them answers, I have nothing to hide,’” recalled Turan Kislakci, a friend of Khashoggi.

If any of these allegations are true, it marks a grave escalation in Riyadh’s campaign of repression against dissidents

Missing Saudi journalist Jamal Khashoggi speaks at an event in London on September 29th, 2018. Photograph: Middle East Monitor/Reuters

Turkey appears to believe Khashoggi was killed at the consulate. Although Ankara has not released any information on its investigation, reports attributed to Turkish officials say the Saudi writer’s body was dismembered, removed in boxes and flown out of the country. Another theory is that he has been abducted but may still be alive.

If any of these allegations are true, it marks a grave escalation in Riyadh’s campaign of repression against dissidents – an escalation that must be met with a strong international response. Khashoggi was for many years a quasi-spokesman for the Saudi monarchy, but since last year he had been living in self-imposed exile, in part due to the rise of Prince Mohammed. In his columns in the Washington Post and elsewhere, he had criticised the Saudi bombardment of Yemen, its diplomatic spat with Canada and the arrest of women’s activists – all three of which have occured on the crown prince’s watch. If Riyadh was responsible for Khashoggi’s death, it was surely intended as a signal to every one of its critics that they will be hunted down wherever they are.

France and the US have called for Saudi Arabia to explain what happened. Unfortunately, Washington cannot be trusted to lean on its chief ally in the Middle East. President Trump has forged a close relationship with the monarchy, and his son-in-law Jared Kushner is friendly with Prince Mohammed. That puts a greater onus on other western powers, and on Turkey itself, to demand answers from Riyadh and to hold it to account.