Up to fifty persons have been arrested in northwestern Iran, days ahead of the annual gathering at a historic fortress in Eastern Azarbaijan province, human rights activists report.

Fort Babak (Qal’a Babak in Persian), originally from the Sassanid era (224-651), is a monumental citadel and National Symbol of Iranians on the top of a mountain in the Qaradaq (Black Mountain) forests, located six km southwest of Kaleybar City in northwestern Iran.

The fortress is believed to have been the stronghold of Babak Khorramdin (795-838 AD), the commander of the Khurramites in Iran who fought for Persian ways of life and independence of his motherland against the Islamic caliphate of Abbassids, based in Baghdad.

Babak was eventually betrayed, handed over to the Abbasid Caliph, al-Mu’tasim, and tortured to death.

In recent years, thousands of Iranians, mostly Azeri speaking activists, gather at Babak Fortress usually during the first weekend in July for the annual commemoration of Babak Khorramdin, celebrating his birthday.

The Islamic Republic authorities every year try to prevent the gathering, which takes the overtones of both Azeri and Iranian patriotism.

According to Human Rights Activists News Agency (HRANA), most of the detainees were arrested in mainly Azeri speaking provinces of Ardabil, West and East Azarbaijan.

“The arrests took place in several cities, including Tabriz and Ahar in East Azerbaijan province and Meshgin Shahr in neighboring Ardabil province,” HRANA reported.

Furthermore, based on HRANA’s report, “Security officials contacted scores of activists and warned them to stay away from the annual ceremony. Dozens of other activists were also summoned and threatened with arrest if they attend the annual ceremony.”

Footage and images circulated in social media show that the gathering took place on July 5 and 6, while the security forces along with intelligence agents and plainclothesmen outnumbered people visiting the fortress.