Concerns have been raised about a prominent member of Saudi Arabia’s royal family after claims she was being detained without charge in a notorious prison used to house al-Qaeda militants.

In a series of tweets published on her verified Twitter account late on Thursday, Princess Basmah bint Saud bin Abdulaziz al-Saud said her health was failing inside a maximum security prison near Riyadh.

“I am currently being arbitrarily held at al-Ha’ir prison without criminal, or otherwise any, charges against my person,” her tweet said. “My health is deteriorating to an extent that is [severe] and that could lead to my death.”

The tweets said she was “abducted without an explanation” with one her daughters and “thrown into prison”, and had been denied medical care, but did not specify dates. A family friend told The Independent that she was locked up with her daughter Suhood.

“I am beseeching my uncle, Custodian of the Two Holy Mosques, King Salman bin Abdulaziz al-Saud, and my cousin, Crown Prince Mohammed bin Salman, to review my case, and to release me as I have done no wrong. My current health status is VERY critical.”

Princess Basmah’s tweets, in which western politicians – including the US president, Donald Trump, and the French foreign minister, Jean-Yves Le Drian – were tagged, were deleted early on Friday afternoon.

However, two sources close to the family of the princess confirmed the authenticity of the tweets and that she was in a high-security lock-up with common criminals and alleged terrorists.

“Someone in Saudi Arabia hacked the account and deleted the tweets,” a friend and former business partner of the princess told The Independent. “We are trying to get them back as we speak right now.”

Two sources close to the family confirmed that she is suffering various ailments that have worsened during her time in prison, where at least two cases of the novel coronavirus have been reported.

“She has some preconditions of a respiratory nature and that’s why we are concerned,” one source said.

Saudi Arabia has been backsliding on human rights since the ascent of de facto ruler Crown Prince Mohammed bin Salman, who has been described as reckless and ruthless. On Tuesday, the human rights organisation Reprieve reported that the rate of executions inside the kingdom had nearly doubled to 800 in the five years since the prince and his elderly father took power in 2015, compared with 423 during the previous five-year period.

Following the abduction, torture, murder, dismemberment and disappearance in 2018 of Jamal Khashoggi, a journalist for The Washington Post, the kingdom has sought to revamp its image. On Thursday, the oil-rich kingdom pledged $500m (£400m) to help global organisations fight the coronavirus pandemic.

Someone in Saudi Arabia hacked the account and deleted the tweets. We are trying to get them back as we speak right now Friend and former business partner of the princess

The princess is an outspoken descendant of the kingdom’s founder, and the youngest daughter of former king Saud bin Abdulaziz al-Saud, who was overthrown in 1964. In a 2012 interview with The Independent, she spoke out against the religious police, restrictions imposed on Saudi women, and the treatment of the kingdom’s religious minorities.

“It is such a non-tolerant atmosphere, even of other sects,” she said. “Any other sect that doesn’t actually belong to our community is thought to be – I’m not going to be sharp but very specific – not the true Islam.”

She has been missing since last year. Prince Mohammed has been rounding up, jailing, and shaking down for money members of the royal family he perceives as opposed to his quest for absolute power.

“They are fighting each other,” said Yahya Assiri, a Saudi dissident living in exile in London. “The royal family is fighting each other over very silly things, They feel jealous of each other over money, property and power.”