Iran’s supreme leader Ayatollah Ali Khamenei said Sunday that Saudi Arabia would face "divine revenge" over its execution of a top Shiite cleric Nimr al-Nimr. Khamenei also called the execution a political mistake by the Saudi government, according to media reports.

"The unjustly spilt blood of this martyr will have quick consequences," Khamenei told clerics in Tehran, after Iranian protestors attacked the Saudi Arabia’s embassy in the city Saturday. According to reports, demonstrators ransacked set the Embassy in Tehran on fire, and crowds broke furniture and smashed windows before being cleared out by police. 

Iranian officials said that 40 people have been arrested following the attack.

"The Saudi government supports terrorist movements and extremists, but confronts domestic critics with oppression and execution," Iranian foreign ministry spokesman Hossein Jaber Ansari reportedly said, warning that the Saudi will have to "pay a high price for following these policies."

Meanwhile, Saudi Arabia’s foreign ministry spokesman Mansur al-Turki called Iran's reaction "irresponsible" and summoned Iran’s envoy to protest the burning of the country’s embassy.

On Saturday, Saudi Arabia executed 47 people, including top Shiite cleric Sheikh Nimr al-Nimr for reasons ranging from joining terrorist organizations to adopting the radical "takfiri" ideology. The country denied discriminating against Shiites and blamed Iran for stirring up unease in the kingdom.

Nimr had long been regarded as the most vocal Shiite leader in the oil-rich kingdom, willing to publicly criticize the ruling family and call directly for elections.

The U.S. State Department said Sunday that the execution would exacerbate sectarian tensions in the region.