Another Muslim preacher has been tortured to death by the Saudi regime as Crown Prince Mohammed bin Salman’s crackdown on preachers and intellectuals intensifies, a rights group says.

Cleric Sheikh Suleiman al-Doweesh lost his life due to severe torture while being subjected to criminal investigations by the Saudi regime, the independent, non-governmental rights group, Prisoners of Consciousness, announced on Tuesday.

Details on the actual circumstances of his death and imprisonment have not been released, as is customary for the Saudi regime to restrict such reliable information.

The news came only two days after Saudi authorities arrested Shaikh Nasser al-Omar, a former professor at the Faculty of Fundamentals of Religion at Riyadh-based Imam Muhammad ibn Saud Islamic University, and suspended his Twitter account.

Since last year, the kingdom has gone on an arrest spree of oppositionists and human rights activists, accusing them of destabilizing efforts and endangering national security.

Bin Salman is accused of using the arrest campaign to muffle all opposition before rising to power.

Saudi officials have also intensified security measures in the Shia-populated and oil-rich Eastern Province, whose residents have undergone peaceful demonstrations since February 2011.

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.