Senior Saudi Prince Miteb bin Abdullah, a former National Guard head once seen as a contender to the throne, has been freed after more than three weeks in detention, according to Twitter messages by royal family members on Tuesday.

Miteb was among dozens of royal family members, ministers and current and former senior officials who were rounded up earlier this month in a "graft purge" at least partly aimed at strengthening the power of Crown Prince Mohammed bin Salman.

It was not immediately possible to confirm the reports of his release and Saudi officials had no immediate comment.

"Almighty, thanks be to you..." wrote Abeer bint Khaled bin Abdullah in a posting on her Twitter account. 

Posting an apparent file photo of Prince Miteb, she added: "May God give you long life, long life full of health, and keep you for us."

Writing on his Twitter account, Moaid Mahjoob, who identifies himself as director of external relations for Princess Jawahar Al-Saud, another Saudi royal family member, said Prince Miteb "had been released and that he was at his home in Riyadh."

Another royal family member, Princes Nouf bint Abdullah bin Mohammed bin Saud, also posted a similar message on Twitter, writing over a photo of Prince Miteb, "May you be safe for us, Abu Abdullah."

The posting of a photo and thanksgiving to God indicates the author of the Tweet believes Prince Miteb has been freed.

Before he was sacked by a royal decree on November 4, Miteb headed the Saudi National Guard, an elite internal security force originally based on traditional tribal units that was run by his father for five decades.