The arrests were accompanied by an announcement that King Salman was placing his son, Mohammed, in charge of restructuring the Saudi intelligence apparatus - a move that all but ended speculation that the crown prince would be sanctioned.
Appearing on a discussion panel at an global investment conference in Riyadh, Crown Prince Mohammed bin Salman said all culprits would be punished, and that Saudi Arabia and Turkey would work together "to reach results".
In this Saturday, May 20, 2017 file photo, President Donald Trump shakes hands with Mohammed bin Salman during a bilateral meeting in Riyadh. Saudi Arabia and Iran are engaged in what amounts to a proxy war in Yemen, where they are supporting opposing sides in a bloody civil war.
Turkish officials say the 15 men comprised a Saudi hit squad that included a member of Prince Mohammed's entourage on overseas trips.
President Donald Trump criticized the "cover-up" of the murder of Saudi journalist Jamal Khashoggi in a statement to a reporter Tuesday, and the State Department said the US would take action against Saudi Arabia.
For Saudi Arabia's allies, the burning question has been whether they believe that Prince Mohammed, who has painted himself as a reformer, has any culpability in the killing, a possibility raised by several US lawmakers.
The crown prince is likely to appear on a panel alongside Lebanon's prime minister-designate Saad Hariri, whose resignation in a televised address from the Saudi capital in mysterious circumstances previous year sparked rumours he was being held against his will. The Turkish head refuses to provide it to Americans.
A statement by Saudi Attorney General Saud al-Mojeb attributed the latest findings of a joint Turkish-Saudi investigation to information from Turkish counterparts.More news: Devil worship schoolgirls 'in satanic plot to murder classmates'
In an immediate analysis of the rationale behind President Erdogan's unexpected diplomatic deference to the Saudi king, Martin Chulov, the Guardian's Middle East correspondent, said: "Erdogan clearly calculated that it did not suit him, or Turkey, to release the audio of the killing, and apparent video - both of which multiple sources have confirmed that his officials indeed have".
Still, neither Trump nor Saudi Arabia have been willing to implicate Saudi leadership in the journalist's killing.
Turkish President Recep Tayyip Erdogan says he wants Saudi Arabia to allow 18 suspects that it detained for the journalist's killing to be tried in Turkish courts.
Erdogan also claimed that security cameras at the Saudi consulate in Istanbul were disconnected hours before Khashoggi arrived for his appointment to obtain paperwork for his planned marriage.
"We're going to know a lot over the next two days about the Saudi situation", he added.
Saudi Arabia has said he was killed in a fistfight at the consulate.
Turkey suspects Mr Khashoggi, 59, was dismembered inside the consulate.
Shortly after Trump spoke, Secretary of State Mike Pompeo said the US would punish certain Saudis who have been connected to the killing. He is never heard from by his friends or family again.