Turkish President Tayyip Erdogan on Monday called on Riyadh to prove its claim that Saudi Arabian journalist Jamal Khashoggi, who has been missing since last week, left the Saudi consulate in Istanbul, while the Washington called on Saudi Arabia to support an investigation into his disappearance, Reuters reported.

The disappearance of Khashoggi, previously a prominent newspaper editor in Saudi Arabia and an adviser to its former head of intelligence, has sparked global concern, particularly after Turkish sources said over the weekend that authorities believed he was killed inside the consulate.

Khashoggi left Saudi Arabia last year, saying he feared retribution for his criticism of Saudi policy in the Yemen war and its crackdown on dissent. He entered the consulate in Istanbul last Tuesday to get documents for his forthcoming marriage. Saudi officials have said that he left shortly afterwards but his fiancée, who was waiting outside, said he never appeared.

“We have to get an outcome from this investigation as soon as possible. The consulate officials cannot save themselves by simply saying ‘he has left’,” Erdogan told a news conference in Budapest, where he is on an official visit.