People inside the royal court also told Middle East Eye that the scale of the crackdown, which has brought new arrests each day, is much bigger than Saudi authorities have admitted, with more than 500 people detained and double that number questioned.
Members of the royal family, government ministers and business tycoons were caught up in the sudden wave of arrests orchestrated by Crown Prince Mohammed bin Salman, known as MBS, under the banner of an anti-corruption drive.
Some, but not all, of the top figures arrested were singled out for the most brutal treatment, suffering wounds to the body sustained by classic torture methods. There are no wounds to their faces, so they will show no physical signs of their ordeal when they next appear in public.
Some detainees were tortured to reveal details of their bank accounts. The source is unable to report specific details about the abuse they suffered in order to protect the anonymity of its sources.
The purge, which follows an earlier roundup of Muslim clerics, writers, economists and public figures, is creating panic in Riyadh, the Saudi capital, particularly among those associated with the old regime of King Abdullah, who died in 2015, with power then passing to his half-brother, King Salman.
Many fear the primary purpose of the crackdown is a move by MBS to knock out all rivals both inside and outside the House of Saud before he replaces his 81-year-old father.
On Wednesday night, seven princes were released from the Ritz-Carlton Hotel in Riyadh, where they had been held since Saturday. The top royals have been moved to the king’s palace, according to the source.
The crown prince’s cousin, Mohammed bin Nayef, who continues be under house arrest, has had his assets frozen, media report said. Sons of Sultan bin Abdulaziz have also been arrested and had their assets frozen.
One of the most famous is Prince Bandar bin Sultan, a former Saudi ambassador to Washington and confidant of former US president George W Bush.
There is no word on his fate, but Saudi authorities said that one of the corruption cases they are looking at is the al-Yamamah arms deal, in which Bandar was involved.
Bandar bought a hamlet in Oxfordshire, in a picturesque area of central England, and a 2,000-acre sporting estate with part of the proceeds from kickbacks he received in the al-Yamamah arms deal, which netted British manufacturer BAE £43bn ($56.5bn) in contracts for fighter aircraft.
As much as $30m (£15m) is alleged to have been paid into Bandar’s dollar account at Riggs Bank in Washington and the affair led to corruption probes in the US and UK, although the case was dropped in the UK in 2006 after an intervention by then-prime minister Tony Blair.
Also among those arrested is Reem, the daughter of Al-Waleed bin Talal, the only woman to be targeted in the latest roundup.
To prevent others from fleeing, MBS has ordered a freeze on private bank accounts. The number of account closures and those banned from travel is many times the number of people who have been arrested, the sources in Riyadh said.
No one expected a crackdown of this scale and against princes of such seniority in the House of Saud, which is why so many of those detained were caught red-handed and had no time to flee.
The purge against other members of the royal family is unprecedented in the kingdom’s modern history. Family unity, which guaranteed the stability of the state since its foundation, has been shattered.
The last event of this magnitude was the overthrow of King Saud by his brother Prince Faisal in 1964. At one point in that saga, Prince Faisal ordered the National Guard to surround the king’s palace, but the king himself was never vilified.
His exit was dignified and all the senior figures, including Faisal himself, waved him goodbye at the airport.
Mohammed bin Salman vowed before becoming crown prince, "I confirm to you, no one will survive in a corruption case - whoever he is, even if he’s a prince or a minister.”
Today, however, the sons of all four key men in the House of Saud who comprised the core of the family through the last four decades have been targeted. They are the sons of King Fahd bin Abdulaziz, King Abdullah, Prince Sultan and Prince Nayef.
This represents an unprecedented attack on the position and wealth of the pillars of al-Saud, including the three most prominent figures of the ruling Sudairi clan.
King Salman is one of seven Sudairi brothers, the clan that has dominated the kingdom for the last 40 years. The other surviving Sudairi is Ahmed bin Abdulaziz, who has been sidelined.
Salman only gained the throne because two of his four full brothers, Sultan and Nayef, died as crown princes.
Even then his accession was a close-run thing, as reported previously. King Abdullah died before a decree writing Salman out of the line of succession could be signed and published.
In Bedouin culture, the attack on his cousins will not be forgotten or forgiven. Their public humiliation, as well as the freezing of their assets, is seen as a blow to their honor, which surviving members of their family are duty bound to avenge.
The crown prince’s attack on leading business figures is equally risky.
One of those rounded up on Saturday was Bakr bin Laden, the head of Saudi Arabia’s biggest construction company. He had managed the biggest construction programs for decades through a series of sub-contractors he paid directly.
Bin Laden was rich enough to absorb the costs, before he in turn had to "bribe” officials in the government to get paid for the original work and the contract they had agreed.
Once you remove the man or the company at the top of the sub-contractor pyramid, no one beneath him gets paid, thus risking throwing the entire construction industry into disarray. The same happened to Saudi Oger, the company owned by Saad Hariri, the former prime minister of Lebanon, which was declared bankrupt on 31 July.
Some of the ministers MBS promoted have also been caught by the purge.
Adel Fakeih, a former minister of planning and the economy, spearheaded the rollout of bin Salman’s ambitious privatization drive called Vision 2030.
He was also key in the announcement of Neom, a proposed mega-city backed by $500bn in government money to be built on the shores of the Red Sea.
Fakeih, a former mayor of Jeddah, was arrested on 4 November. The same fate was suffered by Adel al-Torifi, the crown prince’s information minister.
Symbolically, the announcement of Neom was made at the Ritz Carlton hotel, where the princes have been detained since Saturday.
Many of Mohammed bin Salman’s colleagues must now be asking themselves how long they have before the ambitious prince turns on them.
By hitting the foundations of the unity of the family, as well as the oligarchs, and targeting independent scholars and public figures, MBS is turning his guns on the traditional pillars of the Saudi state, one analyst said.
"So far, the Saudi kingdom has used chaos as a policy in its near abroad, either in Iraq, Syria or in Yemen. However, it is now implementing the chaos theory at home too, and no one, least of all the prince himself, can be sure of what will now happen,” an informed person in Riyadh said last night.
"The stability of the kingdom was built on three pillars: the unity of the al-Saud family, the Islamic character of the state and the flourishing loyal domestic business community. By hitting all three simultaneously, the risk of the kingdom sinking into the sand is very high,” he said.