ISTANBUL -- The Washington Post published a surveillance image Tuesday showing its missing Saudi contributor walking into the Saudi Consulate in Istanbul a week ago, just before he disappeared. Turkish officials have said they fear the columnist was killed there, and announced on Tuesday that they would be searching the consulate as part of their ongoing investigation into Khashoggi's disappearance.

Saudi Arabia has called the allegations that it killed writer Jamal Khashoggi "baseless," but has offered no evidence over the past seven days to show that he ever left the building.

In a statement issued Tuesday, Turkish Foreign Ministry spokesman Hami Aksoy said Saudi authorities had notified Ankara that they were "open to cooperation" and would allow the consulate building to be searched. The ministry did not say when the premises would be searched. Officials in Saudi Arabia did not immediately respond to a request for comment.

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The image released by the Post bore a time and date stamp. The Post said "a person close to the investigation" shared the image with them.

Khashoggi, 59, went missing while on a visit to the consulate in Istanbul for paperwork to marry his Turkish fiancée. The consulate insists the writer left its premises, contradicting Turkish officials.

Photo published in Washington Post on October 9, 2018 shows what newspaper says is surveillance video still it got from third party showing missing Saudi journalist and Post contributor Jamal Khashoggi walking into Saudi Consulate in Istanbul on October 2, 2018 -- the last time he was heard from The Washington Post

He had been living since last year in the United States, in a self-imposed exile, in part due to the rise of Prince Mohammed, the son of King Salman.

As a contributor to the Post, Khashoggi has written extensively about Saudi Arabia, including criticizing its war in Yemen, its recent diplomatic spat with Canada and its arrest of women's rights activists after the lifting of a ban on women driving. All those issues have been viewed as being pushed by Prince Mohammed, who similarly has led roundups of activists, businessmen and others in the kingdom.

The Committee to Protect Journalists (CPJ) has been documenting the increasingly harsh treatment of journalists in Saudi Arabia. It says seven were imprisoned there last year and nine this year.

January 2011 file photo shows Saudi journalist Jamal Khashoggi at World Economic Forum in Davos, Switzerland Virginia Mayo / AP

"The worrying trend that we see is a crackdown on critical and independent journalism in Saudi and about Saudi," Robert Mahoney, Deputy Executive Director of CPJ, told CBS News' Pamela Falk. "It is a very repressive place."

He said it comes as no surprise that Riyad is looking to quash criticism, but this case is beyond the sad but true usual jailing of journalists.

Mahoney said Khashoggi's disappearance is "designed, in a very brutal way, to send a message 'if you speak out against the Saudi government, if it could happen to him, it could happen to you."'

Turkish President Recep Tayyip Erdogan on Monday urged the Saudis to back up their claim that Khashoggi left the consulate.

"Now when this person enters, whose duty is it to prove that he left or not? It is (the duty) of the consulate officials," Erdogan said during a visit to Hungary. "Don't you have cameras and other things? Why don't you prove it, you have to prove it."

Turkey summoned the Saudi ambassador on Sunday to request the kingdom's "full cooperation" in the investigation, a Foreign Ministry official said. The Turkish private NTV television said Ankara asked for permission for its investigators to search the consulate building, but a Foreign Ministry official would not confirm the report. The officials spoke on condition of anonymity because they were not authorized to talk to reporters about the subject.

Ties between Ankara and Riyadh are at a low point over Turkey's support for Qatar in its year-long dispute with Saudi Arabia and other Gulf nations. Turkey sent food to Qatar and deployed troops at its military base there.

A Sunni power, Saudi Arabia is also annoyed by Ankara's rapprochement with the kingdom's Shiite archrival, Iran.