Two Saudi princesses claim they have been starved for 60 days after going public about their 13-year confinement in a palace in the royal compound in Jeddah.
The daughters of Saudi Arabia's King Abdullah claim to have fallen out of favour after speaking out against the abuse of women in the kingdom.
Princesses Sahar, 42, and Jawaher, 38, claim that they are imprisoned in mansions in the royal compound in Jeddah, and two of their sisters are held in another mansion nearby.
They said that they were unable to leave the compound and the internet was their only window on the world. In recent weeks they said their situation had deteriorated, with water and electricity cut off for days and even weeks, and no food provided.
"It's a horrible situation, it's a forced famine basically. They are confining us, depriving us of food and water, freedom and rights. We are struggling, we are surviving, we are resisting, we are trying our best to stay alive," Sahar told RT by Skype.
"How can we continue living like this? We have to take the risk of [speaking out]."
The mother of the women, Alanoud Al-Fayez, who moved to London after divorcing King Abdullah, has appealed for help from US President Barack Obama.
The Saudi government denies that the women are being held in captivity, and says they can move freely around Jeddah in the company of bodyguards.
In recent interview, Al-Fayez told AFP that the king's treatment of his daughters had become worse since they went public with their story, and that King Abdullah had recently stopped their rare trips outside the palace to buy food and medicine.
Labour MP Katy Clark wrote in the Guardian that she had lobbied the Foreign Office to make representations to the Saudi government on behalf of the girls, which it had so far refused to do.
Saudi Arabia is a key western ally in the Middle East. King Abdullah, who was crowned in 2005, is one of the world's richest men, with a fortune estimated at $17 billion. He is believed to have 38 children with several different wives.
Sahar said that she and her sisters had enjoyed a pampered adolescence, but had been placed under gradually closer confinement after criticising the country's inequality.
"The king and his sons need to answer these questions: What are we charged with? What exactly is our crime?" said Sahar.
"What is the crime of 99% of women in this country, who are basically suffering under male guardianship? A male guardian can do whatever he wants; he can cut off everything and she is left with nothing," she said.