Iranian protesters ransacked and set fire to the Saudi Embassy in Tehran on Saturday after Saudi Arabia executed an outspoken Shiite cleric who had criticized the kingdom’s treatment of its Shiite minority.

The cleric, Sheikh Nimr al-Nimr, was among 47 men executed in Saudi Arabia on terrorism-related charges, drawing condemnation from Iran and its allies in the region, and sparking fears that sectarian tensions could rise across the Middle East.

The executions coincided with increased attacks in Saudi Arabia by the jihadists of the Islamic State and an escalating rivalry between the Sunni monarchy and Shiite Iran that is playing out in conflicts in Syria, Yemen and elsewhere. Sheikh Nimr was an outspoken critic of the Saudi monarchy and was adopted as a symbolic leader by Shiite protesters in several Persian Gulf countries during the Arab Spring uprisings.

Saudi officials said the mass execution, one of the largest in the kingdom in decades, was aimed at deterring violence against the state. But analysts said that the grouping of Sheikh Nimr with hardened jihadists was a warning to domestic dissidents that could ripple across the region.