Journalist Jamal Khashoggi. File photo/AP

A court in Saudi Arabia on Monday sentenced five people to death for the killing of Washington Post columnist Jamal Khashoggi, who was murdered in the Saudi Consulate in Istanbul last year.

Saudi Arabia's state-run Al-Ekhbariya TV channel reported that three others were sentenced to prison. All can appeal the verdicts.

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.

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, according to state TV.

After holding nine sessions, the trial concluded that there was no previous intent by those found guilty to murder, according to state TV.

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.