By AYSE WIETING, SUZAN FRASER and JON GAMBRELL, Associated Press

ISTANBUL (AP) — Turkey said Tuesday it will search the Saudi Consulate in Istanbul as it investigates why journalist Jamal Khashoggi vanished there a week ago, an extraordinary probe of a diplomatic post amid Turkish officials' fears the writer had been killed inside the building.

That Saudi Arabia would allow foreigners to enter a consulate and search it shows the growing international pressure the kingdom faces over the disappearance of Khashoggi, a contributor to the Washington Post.

The Saudis have called allegations of any involvement in his disappearance "baseless," but had no immediate comment on Turkey's announcement. It remained unclear when the search would take place.

President Donald Trump and European leaders all have called on Riyadh to explain what happened to the 59-year-old journalist who has criticized the Saudi government. So far, the kingdom has offered no evidence in the past seven days to show that Khashoggi ever left the building, as a new surveillance photo surfaced showed him walking in its main entrance.

"The Saudi Consulate cannot absolve itself of responsibility for this incident by allowing its premises to be searched," said Gulseren Yoleri of the Human Rights Association. "It has to prove that Jamal wasn't oppressed at the consulate and that he left safely."

Secretary of State Mike Pompeo also said U.S. officials have raised the matter with their Saudi counterparts.

"We call on the government of Saudi Arabia to support a thorough investigation of Mr. Khashoggi's disappearance and to be transparent about the results of that investigation," Pompeo said in a statement.

Turkish Foreign Ministry spokesman Hami Aksoy said Saudi authorities have notified Ankara that they were "open to cooperation" and would allow the consulate building to be searched. Such a search would be an extraordinary development, as embassies and consulates under the Vienna Convention are technically foreign soil and must be protected by host nations. Saudi Arabia may have agreed to the search in order to appease its Western allies and the international community.

A surveillance image has surfaced, showing Khashoggi entering the consulate Oct. 2. The picture bore a date and time stamp, as well as a Turkish caption saying that Khashoggi was arriving at the consulate. The Post, which first published the photo, said "a person close to the investigation" shared the image with them, without elaborating. The Turkish newspaper Hurriyet also published the image.

The door Khashoggi used appeared to be the main entrance of the consulate in Istanbul's 4th Levent neighborhood, a leafy, upscale district near the city's financial hub that's home to several other consulates. The consulate has other entrances and exits as well, and Saudi officials insist he left through one of them.

It's unclear which camera the footage came from or who operated it. However, a number of closed-circuit surveillance cameras surround the area. Friends of Khashoggi say Turkish police have taken possession of footage from the neighborhood as part of their investigation.

The Saudis have offered no surveillance footage or evidence to corroborate their claims that Khashoggi left the consulate, and Turkish authorities have not provided evidence to show why they believe the columnist was killed there.

"If the story that was told about the murder is true, the Turks must have information and videotape and other documents to back it up," Fred Hiatt, the Post's editorial page editor, told The Associated Press. "If the story the Saudis are telling, that he just walked out ... after half an hour, if that's true, they ought to have facts and documents and evidence and tapes to back that up."

Hiatt added that the "idea of a government luring one of its own citizens onto its own diplomatic property in a foreign country to murder him for the peaceful expression of his views would be unimaginable."

Khashoggi had gone to the consulate in Istanbul for paperwork to marry his Turkish fiancée. He had been living in the United States since last year, in self-imposed exile, in part due to the rise of Saudi Crown Prince Mohammed bin Salman, who has shown little tolerance for criticism.

As a contributor to the Post, Khashoggi has written extensively about Saudi Arabia, including criticism of 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. Those policies are all seen as initiatives of the crown prince, who has also presided over a roundup of activists and businessmen.

The U.N. human rights office said Khashoggi's disappearance is "of serious concern." Spokeswoman Ravina Shamdasani said in Geneva that it would be "truly shocking" if reports of his death are confirmed.

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 while visiting Hungary. "Don't you have cameras and other things? Why don't you prove it? You have to prove it."

Ties between Ankara and Riyadh are at a low point over Turkey's support for Qatar in that country's yearlong dispute with Saudi Arabia and other Gulf nations. Turkey sent food to Qatar and deployed troops at its military base there as the other nations imposed a boycott on the wealthy Gulf country. Meanwhile, Turkey's support of Islamists also has riled Gulf Arab nations, who view groups like the Muslim Brotherhood as a threat.

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

Saudi Arabia is a longtime ally of the United States, but on Monday senior U.S. officials expressed alarm over Khashoggi's disappearance.

Trump, who took his first overseas trip as U.S. president to the kingdom and whose son-in-law Jared Kushner has close ties to Prince Mohammed, said while he had not yet talked to the Saudis about Khashoggi.

"But I will be at some point," he said Tuesday, without elaborating.

Fraser reported from Ankara, Turkey, and Gambrell reported from Dubai, United Arab Emirates. Associated Press writer Walter Ratliff in Washington contributed.