Abdullah Al-Ouda, son of the Saudi preacher Salman Al-Ouda, revealed on Thursday that his father "lost almost half of his ability to hear and see" in prison.
Of his father, Al-Ouda's son tweeted: "Praying for the harmony of hearts and the good of people cost this man his freedom, and made him victim to harm, torture, pressure and denial of treatment, while being placed in solitary confinement since his arrest (more than three years and few months)."
He continued: "A prison doctor told him that he lost almost half of his ability to hear and see! But they still want to harm him!"
There was no immediate comment from the Saudi authorities on the allegations made by Al-Ouda's son. However, the Saudi state usually reiterates its full respect for human rights and prisoners' rights.
In September 2017, the Saudi authorities arrested prominent preachers and activists in the country, most notably Salman Al-Ouda, Awad Al-Qarni and Ali Al-Omari, on charges of "terrorism and conspiracy against the state", amid calls made by international and Islamic personalities and organisations for their release.