"Public prosecution received information from the Turkish side through the Joint Working Group between the Kingdom of Saudi Arabia and Turkey that indicates that the suspects in that incident had done their act with a prior intention", the statement said.
CIA Director Gina Haspel visited Ankara on Tuesday for talks, with Turkish pro-government media claiming on Wednesday intelligence officials shared evidence with her.
Prince Mohammed bin Salman vowed to punish those responsible for the crime, but media reports have quoted Turkish security sources as saying the operation was run by a top aide to the crown prince. A senior intelligence official and an adviser to Prince Mohammed were also removed from their jobs.
Turkish authorities, including the president, said this week that Saudi agents had scouted Istanbul's Belgrad Forest before Khashoggi's death inside Saudi Arabia's Istanbul consulate on October 2.
In the U.S. he wrote a monthly column in the Washington Post in which he criticised the policies of Crown Prince Mohammad bin Salman.
Dampening speculation he could be pushed aside, the prince appeared relaxed, ebullient and conciliatory toward Turkey, which has stopped just short of blaming him for the killing.
The Saudi government admitted Thursday that Khashoggi's killing was planned ahead of time.
Khashoggi, a known critic of the Saudi crown prince, was a known critic of the crown prince, disappeared after entering the Saudi consulate earlier this month.
How Western allies deal with Riyadh will hinge on the extent to which they believe responsibility for Khashoggi's death lies directly with the prince and the Saudi authorities.
In his first public comments on the matter, bin Salman promised on Wednesday that the killers would be brought to justice.
Over two dozen top officials and executives from the United States and Europe, including U.S. Treasury Secretary Steven Mnuchin and chief executives of big banks, canceled their participation in the conference over the killing of Khashoggi inside the Saudi consulate in Istanbul on October 2.
Saudi Energy Minister Khalid Al-Falih conceded yesterday that the scandal had hurt the kingdom's image.
"We will follow all legitimate means to achieve full justice for Jamal, so as not to wake up to another murdered journalist", the statement said. The two countries, while both allies of the USA, have taken opposing positions on crucial Middle East flash points.
Merkel also raised the dire humanitarian situation in Yemen during the call and urged Saudi Arabia to ensure access for humanitarian aid.