Several key members of the Saudi Royal family are still languishing behind bars almost a year after being imprisoned as part of a palace coup, DailyMail.com can reveal.

As the disappearance and suspected death of journalist Jamal Khashoggi at the hands of a Saudi assassination squad continues to shock the world, the brutal regime is still holding at least three princes and a billionaire businessman arrested as part of a supposed crackdown on corruption last year.

Many fear the five men may have been tortured or killed.

Prince Khaled bin Talal, Prince Turki bin Abdullah Al Saud, and Prince Abdul Aziz bin Fahd are all still behind bars along with billionaire businessman Mohammed Hussein Al-Amoudi, according to three sources close to the royal family.

Locked up: Prince Khaled bin Talal (left) Prince Turki bin Abdullah Al Saud (center) and Prince Abdul Aziz bin Fahd (right) (pictured wearing a ghutrah headdress) remain behind bars after they were arrested during a coup last year. Turki is feared to be dead and Abdul Aziz is rumored to be in a coma

Free: Sources tell DailyMail.com that Prince Alwaleed, the brother of Prince Khaled, was hung upside down and beaten during interrogations but has now been released - but is not allowed to leave the country

Jailed: Businessman Mohammed Hussein Al-Amoudi, who is estimated to be worth $10.6 billion, made his fortune in real estate and oil, has been behind bars since November 2017

Prince Abdul Aziz is rumored to be in a coma, and there are fears that Prince Turki may be dead.

The men were arrested along with several other princes and hundreds of officials during a de-facto coup by Crown Prince Mohammed bin Salman at the end of last year in an attempt to consolidate his power in the kingdom.

Both Al-Amoudi and Prince Turki, whose late father King Abdullah was the ruler of Saudi Arabia, were at first held at the Ritz Carlton in Riyadh.

The hotel was converted to a plush prison for weeks, and the prisoners were later taken to the notorious Al Ha'ir jail nearby.

Prince Turki's chief of staff, who was also detained inside the Ritz Carlton, died in custody with his body showing signs of severe torture.

Prince Khaled bin Talal is alive but remains in custody, friends say, and is only allowed to call his family once a week.

Prince Khaled is the brother of another royal detained in the crackdown, Prince Alwaleed bin Talal, who owns significant stakes in Twitter and has a fortune estimated by Forbes at $17billion.

The men were arrested along with several other princes and hundreds of officials during a de-facto coup by Crown Prince Mohammed bin Salman (pictured wearing a ghutrah) at the end of last year in an attempt to consolidate his power in the kingdom

Sources close to the Saudi royals told DailyMail.com that Prince Alwaleed was hung upside down and beaten during interrogations at Al Ha'ir, and has now been released but is not allowed to leave the country.

One source who works closely with several Saudi royals, said some detainees at the Ritz Carlton were beaten and electrocuted, and even those who are currently not in prison are forced to wear ankle bracelets, including Prince Alwaleed.

Crown Prince Mohammed bin Salman is suspected to be responsible for the death of Washington Post columnist Jamal Khashoggi

Al-Amoudi, who is estimated to be worth $10.6 billion, made his fortune in real estate and oil, and has been estimated by Forbes to be Saudi Arabia's second richest citizen.

He has remained in prison since his arrest in November 2017.

Middle East expert Simon Henderson, a senior fellow at think tank the Washington Institute, said the detainees now have few options.

'I think they're stuck there. Their only hope is somehow Prince Mohammed thinks it's necessary to show some sort of human aspect in trying to distance himself from the Khashoggi incident. They might get out in those circumstances,' Henderson said.

'But I don't think he is someone who admits to his mistakes and when it comes to politics, he doesn't believe in compromise or generosity.'

Khashoggi, a columnist for the Washington Post, is widely believed to have become the latest victim of the brutal Saudi regime.

The government in Turkey claims to have evidence that US-based journalist Jamal Khashoggi was murdered at the Saudi Arabia embassy after the critic of the country went to get a visa for his upcoming wedding.

Detainees who were taken to the Ritz-Carlton in Riyadh were beaten and electrocuted, according to one source. Both Al-Amoudi and Prince Turki were at first held at the hotel

He was captured on CCTV footage entering the building in Istanbul October 2 and a source has told The Washington Post he was killed and then dismembered by members of security.

'The voice recording from inside the embassy lays out what happened to Jamal after he entered,' the insider told the newspaper.

'You can hear his voice and the voices of men speaking Arabic … You can hear how he was interrogated, tortured and then murdered.'