A Turkish official says the Saudi ambassador to Turkey has been summoned to the ministry for discussions over a Saudi journalist who disappeared after a visit to the Saudi Consulate in Istanbul.
The Foreign Ministry official says the ambassador was "invited" to the ministry on Thursday but did not provide further detail.
Jamal Khashoggi, who has written Washington Post columns critical of the kingdom's assertive crown prince, went missing on Tuesday.
He went to the Saudi consulate to receive an official document for his marriage and has not appeared since then.
Turkish and Saudi authorities have given conflicting accounts about the whereabouts of Khashoggi.
After an initial period of silence, Saudi Arabia said the consulate was working with Turkish authorities "to uncover the circumstances of the disappearance of Jamal Khashoggi after he left the consulate building".
Turkish presidential spokesman Ibrahim Kalin, however, told reporters on Wednesday the journalist was being held at the consulate, adding that Ankara was in touch with Saudi officials.
The US State Department said it was investigating the matter.