Protesters hold pictures of missing journalist Jamal Khashoggi during a demonstration in front of the Saudi Consulate in Istanbul on Monday. (Ozan Kose/AFP/Getty Images)

Turkish President Recep Tayyip Erdogan demanded Monday that Saudi Arabia prove that journalist Jamal Khashoggi left the Saudi Consulate in Istanbul on his own, as Saudi officials have repeatedly asserted, after he disappeared last week while inside the mission.

Erdogan’s comments were his most direct suggestion yet of potential Saudi culpability in Khashoggi’s disappearance. But other Turkish officials have said they believe that Khashoggi was killed by Saudi agents inside the consulate.

“Do you not have cameras and everything of the sort?” Erdogan said of the consular officials. “They have all of them. Then why do you not prove this? You need to prove it.”

Turkey’s Foreign Ministry summoned the Saudi ambassador to urge “full cooperation” in the investigation into Khashoggi’s disappearance, the official Anadolu news agency said Monday.

The ambassador was called to the ministry in the Turkish capital, Ankara, on Sunday, the agency said. It was the second time Turkey summoned the ambassador since Khashoggi failed to emerge after a visit to the consulate on Oct. 2.

Turkish officials have said they believe Khashoggi, 59, a critic of the Saudi leadership and a contributor to The Washington Post’s Global Opinions section, was killed by a team of 15 Saudis flown in specifically to carry out the attack. Saudi authorities have called the allegation “baseless.”

In his first remarks about the disappearance, President Trump told reporters Monday afternoon that he was concerned. “I don’t like hearing about it. Hopefully that will sort itself out. Right now, nobody knows anything about it, but there’s some pretty bad stories going around. I do not like it,” Trump said.

Secretary of State Mike Pompeo, in a statement issued late Monday, said that “we have seen conflicting reports on the safety and whereabouts” of Khashoggi. Repeating Trump’s expression of “concern,” Pompeo, who had just returned from a trip to Asia, called on the Saudi government “to support a thorough investigation of Mr. Khashoggi’s disappearance and to be transparent about the results of that investigation.”

Turkey has yet to make any evidence public. The private Turkish broadcaster NTV reported Monday that police had requested access to the Saudi Consulate. It was unclear whether the police were granted access or whether they would search the diplomatic mission in Istanbul’s Levent district at a later date.

A report Monday in the daily newspaper Sabah said investigators were also focused on a convoy of diplomatic vehicles that departed from the consulate on the day Khashoggi vanished. A U.S. official said that Turkish investigators believe Khashoggi was probably dismembered and his body removed in boxes and flown out of the country.

Members of Congress, where there has long been bipartisan skepticism about Saudi Arabia, have issued statements and tweets demanding answers from Riyadh. Sen. Lindsey O. Graham (R-S.C.) said in a string of tweets Monday that “if there is any truth to the allegations of wrongdoing by the Saudi government it would be devastating to the US-Saudi relationship and there will be a heavy price to be paid—economically and otherwise.”

Graham, who played golf Sunday with Trump at the president’s course in Sterling, Va., said that he had consulted with Senate Foreign Relations Committee members Bob Corker (R-Tenn.) and Benjamin L. Cardin (D-Md.) over their “shared concerns regarding the whereabouts and treatment” of Khashoggi.

In a statement sent to journalists Monday, Prince Khalid bin Salman, the Saudi ambassador to Washington, said that reports the kingdom had detained or killed Khashoggi were “absolutely false and baseless . . . I don’t know who is behind these claims, or their intentions,” he said, “nor do I care frankly.”

“What we do care about is Jamal’s wellbeing and revealing the truth about what occurred,” the ambassador said. “Jamal has many friends in the Kingdom, including myself, and despite our differences, and his choice to go into his so called ‘self-exile,’ we still maintained regular contact when he was in Washington.”

The Saudi government, he said, was “fully cooperating” in the Turkish government’s investigation. “Jamal is a Saudi citizen whose safety and security is a top priority for the Kingdom.”

In a meeting Sunday night with The Post’s publisher, Fred Ryan, the ambassador said it was “impossible” that such a crime could be covered up by consulate employees “and we wouldn’t know about it.”

Khalid told Ryan that Khashoggi, who was once close to the ruling family in Saudi Arabia, had “always been honest” and that his criticism of the current Saudi leadership “has been sincere.”

During the meeting, Ryan expressed The Post’s “grave concern” about Khashoggi’s disappearance, and said the news organization would view any Saudi government involvement in his disappearance as a flagrant attack on one of its journalists.

Karen DeYoung in Washington contributed to this report.