Saudi Arabia's state-run Al-Ekhbariya TV channel reported that three others were sentenced to prison. All can appeal the verdicts, AP reported.
The crown prince drew international condemnation for the killing because several Saudi agents involved worked directly for him. The kingdom denies that Prince Mohammed bin Salman had any involvement or knowledge of the operation.
State TV also reported the Saudi attorney general's investigation showed that the crown prince's former top adviser, Saud al-Qahtani, had no proven involvement in the killing . Al-Qahtani, however, has been sanctioned by the United States for his alleged role in the operation.
The court also ruled that the Saudi consul-general in Istanbul at the time, Mohammed al-Otaibi, was not guilty. He was released from prison after the verdicts were announced.
After holding nine sessions, the trial concluded that there was no previous intent by those found guilty to murder, the report said.
The trials of the accused were carried out in near total secrecy, though a handful of diplomats, including from Turkey, as well as members of Khashoggi's family were allowed to attend the sessions.
The killing had shocked the world and drawn condemnation from the international community, including the United Nations.
Khashoggi had walked into his country’s consulate in Istanbul on that morning in October 2018 to collect documents that would allow him to wed his Turkish fiancée, Hatice Cengiz, who waited for him outside. He never walk out.
Agnes Callamard, a UN special rapporteur who authored an inquiry into Khashoggi's killing, later said the search for justice must not be left to the Saudi judicial system, which is “so vulnerable to political interference.”
Meanwhile, numerous critics of the Saudi crown prince remain imprisoned and face trial for their acts of dissent.