A Human Rights Monitor has called on Saudi Arabia to immediately investigate the claims that authorities physically mistreated prominent people who were arrested last year, and hold those responsible to account.

The US-based Human Rights Watch statement on Wednesday referred to detainees, including princes, businessmen, and former and current government officials, held late last year.

"The alleged mistreatment at the Ritz Carlton is a serious blow [Saudi crown prince] Mohammad bin Salman's claims to be a modernising reformist," said Sarah Leah Whitson, Middle East director at Human Rights Watch.

"It is great that the Saudi government wants to combat corruption, but its alleged tactics look more like extortion, and make a mockery of the rule of law," Whitson said, "as the new government tries to sell its reformist credentials to the public, governments, and investors, they should take a hard, sceptical look at what actually happened in the Riyadh Ritz Carlton and its implications.

"While MBS jaunts across Western capitals to gin up foreign investments, investors should think twice the Saudis' cavalier dismissal of the rule of law and fundamental rights."

A report by the New York Times on Monday suggested that 17 of the detainees who were mistreated required hospitalisation for physical abuse.

{articleGUID}

They included one who later died in custody, the report said, "with a neck that appeared twisted [and] a badly swollen body and other signs of abuse." It identified Major General Ali al-Qahtani as the man who died in detention.

Human Rights Watch warned at the time that the November 4 mass arrests on corruption allegations raised human rights concerns and appeared to take place outside of any recognisable legal framework, with detainees forced to trade financial and business assets for their freedom. Riyadh's Ritz Carlton Hotel, where many were held, became an unofficial detention centre.

On January 30, Saudi Arabia's attorney general announced that authorities had "subpoenaed" 381 people in the corruption probe, adding all who settled with the government or against whom there was not sufficient evidence, were released.

The government said it had seized over $106bn worth of assets, including "real estate, commercial entities, securities, cash and other assets."

The statement said that 56 people remained in custody "to continue the investigations process."

Late king's sons targeted

The New York Times report identified Bakr bin Laden, chairman of the construction company, Saudi Binladin Group, and Prince Turki bin Abdullah, former Riyadh governor and son of the late King Abdullah, as two of the men who remain in detention.

The report also indicated that in addition to Prince Turki, the corruption probe targeted several other sons of the late King Abdullah.

Saudi Crown Prince Mohammed bin Salman has been told to be the driving force behind the arrests. Prince Mohammed bin Salman has outlined his plans for the kingdom in his Saudi Vision 2030 and the arrests are seen as his efforts to consolidate his authority in the government.

The Human Rights Watch stressed that it documented in the past numerous allegations of torture and ill-treatment in Saudi prisons and detention centres in recent years.

The watchdog also condemned Saudi courts' use of confessions to sentence defendants to serious punishments, including the death penalty, even after defendants tried to recant them in court, saying that they were coerced into giving them.