ISTANBUL — President Recep Tayyip Erdogan of Turkey, turning up the pressure on Saudi Arabia, promised Sunday to reveal everything his country knows about the killing of Jamal Khashoggi inside a Saudi consulate.

Mr. Erdogan’s statement came as the Saudi foreign minister publicly apologized to Mr. Khashoggi’s family, but stuck with his government’s contention that the killing had been a “tremendous mistake” by Saudi operatives acting “outside the scope of their authority.”

Turkish officials have suggested that Mr. Khashoggi’s death was ordered at the highest levels of the kingdom. And Mr. Erdogan, who has commented little on the matter publicly, on Sunday indicated that he has more to say about what happened.

“We said that we will reveal it,” Mr. Erdogan said in a speech broadcast live on Sunday. “God willing, I will make my statement about Jamal Khashoggi in the parliamentary group on Tuesday.”

Mr. Khashoggi, a journalist critical of the Saudi government, disappeared after entering its consulate in Istanbul on Oct. 2. Turkey and Saudi Arabia have conducted what has been described as a joint investigation into Mr. Khashoggi’s disappearance, conducting searches of both the consulate building and the nearby residence of the Saudi consul.

On Saturday, Saudi Arabia announced that Mr. Khashoggi had been killed in a “brawl” inside the consulate, its first acknowledgment that he was dead, and that Saudis were responsible. It said 18 Saudis involved in the case had been detained.

The statement followed weeks of Saudi insistence that Mr. Khashoggi had left the consulate, unharmed, hours after entering.

On Sunday, in an interview with Fox News, Foreign Minister Adel al-Jubeir said, “There obviously was a tremendous mistake made, and what compounded the mistake would be the attempt to try to cover up.”

Asked if he had a message for Mr. Khashoggi’s relatives, Mr. Jubeir said: “This is a terrible mistake. This is a terrible tragedy. Our condolences go out to them. We feel their pain.”

Turkish officials have indicated that the Saudi version — that Mr. Khashoggi died in a botched attempt at interrogation and abduction — does not fully satisfy them.

For several days, Turkish officials speaking anonymously have told news organizations that a team of 15 Saudis flew to Istanbul on Oct. 2 to kill Mr. Khashoggi, most likely on the orders of the crown prince, Mohammed bin Salman. They have even claimed to have recordings of his torture and killing.

“We are searching for justice and it will be revealed in full nakedness,” Mr. Erdogan said on Sunday afternoon, at an event to open a new subway line in Istanbul. “Not with ordinary steps, but in full nakedness.”

“Why did 15 people come here?” he asked. “Why have 18 people been arrested? All of this must be explained with all the details. On Tuesday, I will tell this very differently in my parliamentary group speech. I will go into detail.”

Mr. Erdogan’s comments came as Saudi Arabia was accused of deception in the case by both President Trump and the publisher of The Washington Post, for which Mr. Khashoggi wrote columns.

Mr. Trump, in another shift of tone against Saudi Arabia, expressed doubt about the Saudi government’s claim that Mr. Khashoggi was killed accidentally. “Obviously, there’s been deception and there’s been lies,” Mr. Trump said in a telephone interview with The Post. “Their stories are all over the place.”

Fred Ryan, the paper’s publisher, said the Saudi government had “shamefully and repeatedly offered one lie after another.”

“Offering no proof, and contrary to all available evidence,” Mr. Ryan said on Twitter, “they now expect the world to believe that Jamal died in a fight following a discussion. This is not an explanation; it is a cover-up.”

Mr. Erdogan had been uncharacteristically quiet about the scandal around Mr. Khashoggi’s disappearance, even as a steady stream of leaks from his own government helped the case capture the world’s attention and shook relations between Saudi Arabia and the United States. Yet Mr. Erdogan, who knew Mr. Khashoggi personally and took great affront at how Saudi Arabia handled the affair, did use information gathered by his intelligence services to pressure the Saudis into owning up.

In particular, Mr. Erdogan has aimed some of his ire toward Crown Prince Mohammed, whose firm grip on power in the kingdom has been called into question over the death of Mr. Khashoggi. Mr. Erdogan made an apparent swipe at the crown prince in his speech Sunday.

“And right now, what does the world say about whom?” he said. “We will look into all of this.”

Mr. Khashoggi, who for years was close to the Saudi royal family, became a critic as Crown Prince Mohammed cracked down on dissent, moving to the United States.

Mr. Jubeir, the foreign minister, stuck to his government’s insistence that the kingdom’s leadership did not know of the operation to confront Mr. Khashoggi in the consulate in Istanbul, and that it did not know at first that he had been killed.

He specifically denied that the crown prince knew of the operation ahead of time, “The individuals who did this did this outside the scope of their authority,” Mr. Jubeir said.

It was not until some time after the killing that Saudi leaders realized that their account contradicted the information the Turks had, he said.

“We discovered that he was killed in the consulate,” he said. “We don’t know in terms of details how. We don’t know where the body is.”

Turkish officials have said that Mr. Khashoggi’s body was dismembered by a Saudi forensics expert using a bone saw, and then disposed of. In recent days, investigators have combed through sites, including a forest just outside Istanbul and a farmhouse south the city, looking for evidence of his fate.

In comments published Saturday in the newspaper Hurriyet, Mr. Erdogan said he had expressed his irritation at the Saudi handling of the case to a Saudi delegation sent from Riyadh, and also in a phone conversation with King Salman last week.

He said he had complained about the actions of the Saudi consul, who did not cooperate with Turkish officials but invited a camera crew into the building to show that Mr. Khashoggi was not there. Turkish investigators were not allowed to search the consulate until 13 days after Mr. Khashoggi went there.

“At the end of the day, Saudi Arabia has to shed light on this,” Mr. Erdogan told Hurriyet. “It’s not possible for us to leave this unfinished.”

Pro-government Turkish columnists have been echoing the sentiment that Saudi Arabia should come clean. Several have even called for Crown Prince Mohammed to step down.

“Naturally the U.S.A. and Saudi Arabia are pleased with the development of events — both have the desire ‘Let’s wrap up it as it is,’” one columnist, Mahmut Ovur of the staunchly pro-government daily Sabah, wrote on Sunday.

The crown prince, he wrote, “has no chance to emerge clean from this.”