ANKARA, Oct. 6 (Xinhua) -- The Turkish authorities are conducting a thorough investigation on the disappearance of the Saudi Arabian journalist Jamal Khashoggi after he entered the Saudi consulate in Istanbul.

"There is an ongoing investigation on this foreign individual by the police and affiliate organizations," a Turkish source told Xinhua on condition of anonymity.

The Turkish police said on Saturday that the missing Saudi journalist hasn't left the Saudi consulate.

The Washington Post's columnist Jamal Khashoggi, a Saudi dissident critic of the country's crown prince and a former government adviser, entered the consulate last Tuesday.

His visit to the consulate was related to getting official documents for his re-marriage. But he had reportedly expressed concerns about his safety.

The 59-year-old journalist has been living in self-imposed exile in the United States since he fled the kingdom in September 2017.

Turkey's presidential spokesman Ibrahim Kalin told reporters on Wednesday that Khashoggi remains inside the Saudi consulate, a day after his Turkish fiancee, Hatice Cengiz, reported his disappearance.

"He didn't inform me of a threat or anything of the kind but I felt that he was fearful of something that might concern him. I waited outside the (Saudi) consulate for three hours but he didn't come back, at least I didn't see him coming back," Cengiz told CNNTurk news channel.

Kalin said Turkish Foreign Ministry and police were closely monitoring the case, adding that Ankara was in touch with Saudi officials.

On Thursday, Turkey's Foreign Ministry summoned the Saudi ambassador to Turkey "for consultations" over Khashoggi's disappearance.

In contrasting opinion to the Turkish side, Saudi officials insisted that Khashoggi had left the building.

Saudi Arabia's Crown Prince Mohammed bin Salman welcomed Turkey to search the Saudi consulate in Istanbul.

In an exclusive interview with Bloomberg published on Friday, bin Salman said Saudi Arabia is "very keen to know what happened" to the Saudi citizen, adding "we have nothing to hide."

Turkish and foreign journalists held demonstrations outside the consulate, demanding Saudi authorities shed light on Khashoggi's disappearance for fear of his safety.

The mystery surrounding the missing Saudi journalist happened at a time of strained relations between Turkey and Saudi Arabia, putting the two regional powers at odds.

Saudi Arabia, the United Arab Emirates, Bahrain and Egypt cut ties with Qatar on Jun. 5, 2017, over unsubstantiated claims that Doha has supported extremism and fostered relations with Iran.

When the current Gulf crisis broke out, Turkey sent rapid aid to Qatar including food supplies.

On Jun. 7, 2017, the Turkish parliament ratified a bilateral defense bill previously signed with Qatar.

Last month, Qatari Emir Sheikh Tamim bin Hamad al-Thani pledged 15 billion U.S. dollars investments in Turkey during a visit in Ankara to help its ally to overcome a serious economic volatility.