A renowned Musliminfo-icon preacher and a university lecturer has been declared brain-dead after Saudi officials injected poisonous substance into his body during brutal torture in prison as a crackdown led by Crown Prince Mohammed bin Salman against Muslim preachers and intellectuals widens in the conservative oilinfo-icon-rich kingdom.

The rights group Prisoners of Conscience, which is an independent non-governmental organization seeking to promote human rightsinfo-icon in Saudi Arabiainfo-icon, announced in a post on its official Twitterinfo-icon page that Dr. Ahmed al-Amari, who was a professor at Faculty of the Holy Qur'an in the Islamic University of Madinahinfo-icon, suffered severe brain hemorrhage after the injection.

He was then taken to King Abdullah Medical Complex in the Red Sea port city of Jeddah, where all doctors confirmed that he is brain-dead shortly afterwards.

Also on Monday, Prisoners of Conscience announced that activist Yaser al-Ayyaf is suffering from severe burns and bruises all over his body as a result of savage torture he endured during his detention in solitary confinement.

Saudi Arabia has lately stepped up politically-motivated arrests, prosecution and conviction of peaceful dissident writers and human rights campaigners.

Saudi officials have also intensified security measures in the Shiainfo-icon-populated and oil-rich Eastern Province.

Saudi authorities have brutally tortured political dissident and renowned Muslim preacher Ali Al-Omari in prison.

Eastern Province has been the scene of peaceful demonstrations since February 2011. Protesters have been demanding reforms, freedom of expression, the release of political prisoners, and an end to economic and religious discrimination against the oil-rich region.

The protests have been met with a heavy-handed crackdown by the regime with security forces increasing security measures across the province.

Over the past years, Riyadh has also redefined its anti-terrorism laws to target activism.

In January 2016, Saudi authorities executed Shia cleric, Sheikh Nimr Baqir al-Nimr, who was an outspoken critic of the policies of the Riyadh regime. Nimr had been arrested in Qatif in 2012.