A Saudi Arabian fitness instructor and influencer has been stabbed in the face in prison after being jailed in January for promoting women’s rights on social media.

Manahel al-Otaibi, 30, was sentenced to 11 years in prison for “terrorist offences” in a secret trial that generated widespread criticism, with activists saying it showed the “hollowness” of Saudi progress in human rights.

This week, Manahel told her family she had been stabbed in the face with a sharp pen by an unknown assailant and required stitches. Her family said they had tried to report the attack to the Saudi government’s Human Rights Commission, but were ignored.

Along with her sisters, Maryam and Fawzia, Manahel had been targeted with a campaign of arrests, threats and intimidation after posting messages about female empowerment.

The sisters had been among the first to post using the hashtag #IAmMyOwnGuardian, calling for an end to the male guardianship system dictating that women needed the permission of a husband, father or other male relative to marry or travel.

The authorities accused Manahel of leading a propaganda campaign to incite girls to denounce religious principles, and rebel against customs and traditions in Saudi culture. In November 2022, she was arrested and charged for tweeting in support of women’s rights and posting photos without wearing traditional clothing.

Since she was detained at Al-Malaz prison in the Saudi capital, Riyadh, Manahel has reportedly been brutally beaten by both fellow prisoners and prison guards, and was “forcibly disappeared” for five months when she was allowed no contact with her family between November 2023 and April this year.

“She was very afraid [when we spoke to her by phone], but was strong enough to tell us about the incident and what happened despite their threats to try to keep her silent,” said Fawzia, who narrowly evaded arrest herself by fleeing over the border to Bahrain.

“I believe they are punishing and torturing Manahel because they are unable to punish me,” she said. “She told us that if communication is interrupted again next week [when she is due to call her family again] then it means they have punished her for telling us about everything that happened.”

Lina al-Hathloul, head of monitoring and advocacy at ALQST, which documents human rights in Saudi Arabia, said: “This is the latest in a series of appalling attacks that Manahel has faced in prison, with the Saudi authorities not only turning a blind eye to the abuse but actively facilitating it, including by preventing her from making complaints, placing her in solitary confinement and putting her in cells where she is vulnerable to further violence.

“This is part of a wider pattern in which the authorities are callously toying with the lives of Saudi prisoners of conscience, with potentially lethal consequences.”

Referring to the rise of “sportswashing” by the Saudi regime, Bissan Fakih, at Amnesty Internationalsaid: “When the reality of the human rights situation is camouflaged with sports or entertainment events, it makes it harder for us to pressure the Saudi authorities to release people like Manahel.”

The Saudi embassy in London was contacted for comment.