Funeral prayers for Jamal Khashoggi are being held in Madinah and Makkah on Friday, his son announced on Twitter, suggesting the family has given up hope of recovering his body after more than a month since he was killed in the Saudi consulate in Istanbul.

"The prayer for the absence will be held for the deceased Jamal Khashoggi after Friday prayers at the Prophet's Mosque in Madinah, and after Friday prayers at the Grand Mosque in Mecca," Salah Khashoggi said in a tweet on Thursday.

The elder of Khashoggi's two sons, Salah, 35, left Saudi Arabia for the United States last month. Khashoggi had lived in the US for about a year before his death on October 2.

In an interview with CNN this month, Salah and his brother Abdullah appealed for the return of their father's body.

"All that we want right now is to bury him in Al Baqi [cemetery] in Madinah with the rest of his family," Salah said. "I talked about that with the Saudi authorities and I just hope that it happens soon."

SEE ALSO: U.S. imposes sanctions on 17 Saudis for Khashoggi killing

In an update on Saudi Arabia's investigation into the killing, the Saudi deputy public prosecutor Shaalan Shaalan said on Thursday that Khashoggi's body was dismembered and transported outside of the Saudi consulate in Istanbul.

Mr. Shaalan said 21 people had been arrested in the case and 11 of them were charged with murder. The prosecution was seeking the death penalty for five people who ordered and committed the killing, he said.

Mr. Shaalan said the role of Saud Al Qahtani, formerly an adviser to Crown Prince Mohammed bin Salman, was meeting with the team that was ordered to repatriate Khashoggi.

He said the deputy chief of the Saudi intelligence, General Ahmed Al Assiri, ordered the operation, while the head of the negotiating team that flew to Istanbul to confront Khashoggi had ordered his murder.

Speaking separately, Saudi Foreign Minister Adel Al Jubeir ruled out any involvement of the crown prince in the operation.

"Absolutely, his royal highness the crown prince has nothing to do with this issue," Mr. Al Jubeir told reporters in a press conference in Riyadh.

He said the kingdom was investigating and holding those responsible to account "to make sure this doesn't happen again".

"Sometimes mistakes happen ... sometimes people exceed their authority," he said.

Later on Thursday, the US State Department announced sanctions on Mr Al Qahtani, "his subordinate Maher Mutreb, the Saudi Consul General in Istanbul Mohammed Alotaibi, and 14 other people members of an operations team" with a role in the killing of Khashoggi, who had lived in the US for about a year before his death.

Secretary of State Mike Pompeo said the sanctions were imposed under the Global Magnitsky Human Rights Accountability Act.

"Our action today is an important step in responding to Khashoggi’s killing," Mr. Pompeo said in the statement released by the State Department.

He said the department "will continue to seek all relevant facts, consult Congress, and work with other nations to hold accountable those involved in the killing of Jamal Khashoggi".