The semiofficial ISNA news agency said the country's top police official, Gen. Hossein Sajedinia, rushed to the scene and police worked to disperse the crowd outraged by the execution of Sheikh Nimr al-Nimr. Shiite leaders in Iran and other countries across the Middle East swiftly condemned Riyadh and warned of sectarian backlash.
Saudi Arabia's execution Saturday of 47 prisoners, which also included al-Qaida detainees, threatened to further enflame Sunni-Shiite tensions in a regional struggle playing out between the Sunni kingdom and its foe Iran, a predominantly Shiite nation.
While Saudi Arabia insisted the executions were part of a justified war on terrorism, Iranian politicians warned that the Saudi monarchy would pay a heavy price for the death of al-Nimr.
The Iranian Foreign Ministry summoned the Saudi envoy in Tehran to protest, while the Saudi Foreign Ministry later said it had summoned Iran's envoy to the kingdom to protest the critical Iranian reaction to the sheikh's execution, saying it represented "blatant interference" in its internal affairs.
In Tehran, the crowd gathered outside the Saudi embassy and chanted anti-Saudi slogans. Some protesters threw stones and Molotov cocktails at the embassy, setting off a fire in part of the building, Sajedinia told the semi-official Tasnim news agency.
"Some of them entered the embassy. Currently, individuals who entered the embassy have been transferred out (of the building). However, a large crowd is still there in front of the embassy," Sajedinia told ISNA early Sunday.
Some of the protesters broke into the embassy and threw papers off the roof, and police worked to disperse the crowd, Sajedinia told ISNA. He later told Tasnim that police had removed the protesters from the building and arrested some of them. He said the situation outside the embassy "had been defused."