Saudi Al-Mojeb told journalists in a rare news conference in Riyadh on Thursday that Jamal Khashoggi's killers had set in motion plans for the killing on September 29, three days before The Washington Post contributor was killed inside the kingdom's consulate in Istanbul.
Turkey on Wednesday called for an global investigation into the murder.
President Tayyip Erdogan said recordings related to the killing of Jamal Khashoggi, which Turkey has shared with Western allies, are "appalling" and shocked a Saudi intelligence officer who listened to them, Turkish media reported on Tuesday.
The spokesman said the deputy chief of Saudi intelligence, General Ahmed al-Assiri, had given an order to force Khashoggi home, and "the head of the negotiating team" that flew to Istanbul had ordered his murder.
The prosecutor added that Saudi crown prince Mohammed bin Salman has not been implicated in the murder.
Investigators concluded that Khashoggi was killed after "a fight" that prompted the team to inject him with a sedative.
The journalist's body parts were then handed over to an agent outside the consulate grounds, the spokesperson said.
The prosecutor's statement also appears to exonerate senior Saudi leaders, including Assiri, from the Khashoggi murder. It did not name the five individuals who were sentenced to death.
The prosecutor's office also said it was awaiting Turkey's response to its request for evidence and sound recordings of the crime.