Gregg Zoroya

USA TODAY Opinion

Protesters in Iran, angered at Saudi officials' executions of a prominent Shiite cleric who rallied for political reform and 47 prisoners convicted of terrorism, broke into the Saudi embassy early Sunday, setting fires and throwing papers from the roof, Iranian media reported.

Police worked to disperse the crowd that had gathered late Saturday to express outrage at the execution earlier that day of Sheikh Nimr al-Nimr. Gen. Hossein Sajedinia, the Shiite-majority country's top police official, rushed to the scene, the semi-official ISNA news agency said.

A “huge crowd of people rushed toward the entrance gate of the building passing through resisting police forces and managed to break the gate,” according to Sadra Saeidian of Mehr News.

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Protesters scaled a chain-link fence protecting the embassy, took down the Saudi flag and set fires inside, according to tweets from journalist Sobhan Hassanvand at the privately owned Shargh newspaper. But the angry mob didn't destroy the flag because it is emblazoned with the Muslim statement of faith that Shiites and Sunnis share: "There is no God but Allah and Muhammad is his prophet."

No one appeared to be injured, according to several Iranian media reports.

Also in Iran, demonstrators attacked a Saudi consulate in the city of Mashhad with parts of the building set on fire, China’s official Xinhua news agency reported, citing Persian-media outlet Tabnak.

Tensions remain high in the Middle East between Sunni and Shiite Muslims. Saudi Arabia is a predominantly Sunni nation.

Earlier Saturday the two countries played a diplomatic ping-ping with the Iranian Foreign Ministry summoning the Saudi envoy in Tehran to protest and the Saudi Foreign Ministry saying it had summoned Iran's envoy to protest Iran's critical reaction, calling it “blatant interference” in its internal affairs, according to The Associated Press.

Shiite leaders in Iran and other Muslim countries had condemned Saudi officials after the Saturday executions and warned of sectarian backlash. Human rights and other advocacy groups also voiced their objections.

Iran's supreme leader, Ayatollah Ali Khamenei, posted a series of tweets Sunday morning on @khamenei_ir, his English language account. He said Saudi Arabia will face "divine revenge."

The mass executions — by beheading or shooting — "only further stains Saudi Arabia's troubling human rights record," Sarah Leah, Middle East director for the U.S.-based non-profit Human Rights Watch, told AP.

Saudi Arabia's Ministry of the Interior issued a statement that the 47 condemned men "were involved in a score of terrorist attacks which resulted in deaths of innocent lives and destruction of private, public and military properties," according to the Saudi Press Agency. Several were considered members of al-Qaeda.

A Foreign Ministry statement carried by the official Saudi Press Agency accuses Tehran of "blind sectarianism" and says that "by its defense of terrorist acts" Iran is a "partner in their crimes in the entire region."

United Nations Secretary-General Ban Ki-moon was “deeply dismayed” over the Saudi Arabia executions, including that of Al-Nimr, 56, according to a UN statement.

The U.S. State Department also issued a statement about the executions and al-Nimr.

"We are particularly concerned that the execution of prominent Shia cleric and political activist Nimr al-Nimr risks exacerbating sectarian tensions at a time when they urgently need to be reduced," the statement said. It added that the U.S. has issues with the legal process in Saudi Arabia and that the government there needs to respect human rights and conduct transparent judicial proceedings.

Amnesty International, another human rights organization, decried the death sentences for al-Nimr and other Shiite activists in November, saying, "Saudi Arabian authorities are using the guise of counterterrorism to settle political scores."

In Iraq, Shiite political leader and cleric Moqtada al-Sadr called for demonstrations across the Gulf States to protest the execution of al-Nimr, Reuters reported.

Protests sprang up Saturday in multiple countries in wake of the cleric's execution. Hundreds of his supporters took the streets in his hometown of al-Qatif in eastern Saudi Arabia and in neighboring Bahrain, where police responded with tear gas and bird shot, according to AP.

The sheikh’s brother, Mohammed al-Nimr, said in a telephone interview with AP that Saudi authorities told the family they had already buried the body but didn’t say at which cemetery. The family had hoped to bury his body in his hometown.

Nimr al-Nimr's funeral likely would have attracted thousands of supporters, including large numbers of protesters. Instead the family planned to hold prayers and accept condolences at the mosque in a village near al-Qatif where the sheikh used to pray.

Al-Nimr was a vocal critic of Bahrain’s monarchy, which forcibly suppressed Arab Spring-inspired protests in 2011 with the help of Saudi troops. Popular among disgruntled Shiite youth in Bahrain and Saudi Arabia, al-Nimr never denied the political charges against him but maintained he never carried weapons or called for violence, AP reported.

Jaberi Ansari, foreign ministry spokesman for Iran, said the Saudi government "confronts domestic critics with oppression and execution. ... (It) will pay a high price for these policies," according to media reports. Yemen's Houthi sect, closely linked with Iran, described al-Nimr as a "holy warrior."

In Lebanon, leading Shiite cleric Abdul-Amir Kabalan condemned Nimr al-Nimr’s execution, describing it as “a grave mistake that could have been avoided with a royal amnesty that would have helped reduce sectarian tensions in the region," AP reported.

Kabalan is deputy head of the influential Supreme Shiite Islamic Council that is the main religious body for Lebanon’s 1.2 million Shiites.

The Lebanese Shiite militant group Hezbollah issued a statement calling Nimr al-Nimr’s execution an “assassination” and “ugly crime.”

Of the 47 executed, 45 were Saudi nationals, one was from Chad and another from Egypt. Four were Shiites.

Nimr al-Nimr's nephew, Ali al-Nimr, a juvenile when he was arrested, also is facing execution but wasn't on the list released Saturday. Amnesty International has complained bitterly about juveniles facing the death penalty in Saudi Arabia.

Among those executed was a convicted terrorist involved in a 2004 attack on the U.S. Consulate in Jeddah that left nine dead. Another was Faris al-Shuwail, a leading ideologue in al-Qaeda’s Saudi branch who was arrested in August 2004 during a massive crackdown following the series of deadly attacks, AP reported.

The death of the al-Qaeda militants raises the prospect of revenge attacks. Al-Qaeda's Yemen affiliate last month threatened violence if their sentences were carried out, AP reported.

The executions took place in the capital, Riyadh, and 11 other cities and towns, according to the Saudi Arabian Interior Ministry.

Saudi Arabia carried out 157 executions in 2015, all after King Salman assumed the throne in January. 2014 had 90 executions.

Contributing: The Associated Press