Iran and Saudi Arabia exchanged accusations after the execution of a Shia cleric, and Iran's Ayatollah Ali Khamenei threatened the Saudis with "God's vengeance."
On his website, Khamenei criticized the execution of Shiite imam Nimr Baker al-Nimr, who had led anti-government protests in Saudi Arabia, as well as Saudi-led attacks in Yemen against Shiite rebels and, it said, repression of Shiites in Bahrain, a Saudi ally.
The Iranian leader wrote on Twitter that "without a doubt, the unjustly shed blood of the martyr Sheikh Nimr will quickly cause God's vengeance to hit the Saudi politicians."
Protests were organized in Iran due to the execution of an imam in Saudi Arabia, which is led by a Sunni dynasty, and protesters stormed the Saudi embassy, set it on fire and threw papers from the roof.
On the other hand, the Saudis assessed that statements from Iran testify that the country "supports terrorism".
The Ministry of Foreign Affairs of Saudi Arabia accused Iran of "blind sectarianism" and that "by defending terrorism, Iran becomes complicit in the crimes (of terrorists) throughout the region." The US State Department assessed last night that the execution of 47 people in Saudi Arabia, including Sheikh Nimr, will likely increase tensions in the region.
Iranian President Hassan Rouhani described the attacks on the Saudi Arabian embassy in Tehran and the Saudi consulate in Mashhad in the southeast of the country as "absolutely unjustified".
"Last night's action by a group of extremists in Tehran and Mashhad against the embassy and consulate of Saudi Arabia, which should be legally and religiously under the protection of the Islamic Republic, is completely unjustified," said Iranian President Rouhani, as reported by the official IRNA news agency.
At the same time, Rouhani condemned the execution of Shiite imam Nimr Baker al-Nimr in Saudi Arabia, which sparked last night's violence.
Rouhani called on the Interior Ministry to work with judicial and intelligence authorities to identify the attackers and bring them to justice in order to stop these "terrible actions" and to "ensure the safety of diplomatic missions."
The prosecutor of Tehran announced earlier today that 40 people were arrested in connection with the attack on the Saudi embassy in Tehran, and that four people were arrested in Mashhad.
"The US is calling on Saudi Arabia to allow the expression of discontent," State Department spokesman John Kirby said, adding that Washington is concerned about the executions, which have sparked outrage in the Shiite world.
Saudi Arabia, a traditional US ally, executed 47 people for terrorism, including Imam Nimr al-Nimr, who was sentenced to death in October for rebellion, disobedience and carrying weapons.
El Nimr was a central figure in the Shiite protests that erupted in 2011 as part of the Arab Spring. He was a major critic of the Sunni authorities in Bahrain, which brutally suppressed Shiite protests in 2011. Saudi Arabia sent troops to help the Bahraini authorities fight the protesters, fearing the protests would spread.
Bonus video:
