Iran's top leader on Sunday warned Saudi Arabia of "divine revenge" over the execution of an opposition Shiite cleric while Riyadh accused Tehran of supporting terrorism, escalating a war of words hours after protesters stormed the Saudi Embassy in Tehran.

Saudi Arabia announced the execution of Sheikh Nimr al-Nimr on Saturday along with 46 others, including three other Shiite dissidents and a number of al-Qaida militants. Al-Nimr was a central figure in protests by Saudi Arabia's Shiite minority until his arrest in 2012, and his execution drew condemnation from Shiites across the region.

Iran's Supreme Leader Ayatollah Ali Khamenei condemned the execution Sunday in a statement on his website, saying al-Nimr "neither invited people to take up arms nor hatched covert plots. The only thing he did was public criticism."

Saudi Arabia's Foreign Ministry said that by condemning the execution, Iran had "revealed its true face represented in support for terrorism."

The statement, carried by the official Saudi Press Agency, accused Tehran of "blind sectarianism" and said that "by its defense of terrorist acts" Iran is a "partner in their crimes in the entire region."

Al-Nimr was convicted of terrorism charges but denied ever advocating violence.

Sunni Saudi Arabia and Shiite Iran are locked in a bitter rivalry, and support opposite sides in the wars in Syria and Yemen. Iran accuses Saudi Arabia of supporting "terrorism" in part because it backs Syrian rebel groups, while Riyadh points to Iran's support for the Lebanese Hezbollah and other Shiite militant groups in the region.

The Iranian Foreign Ministry has 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 early Sunday and chanted anti-Saudi slogans. Some protesters threw stones and Molotov cocktails at the embassy, setting off a fire in part of the building, said the country's top police official, Gen. Hossein Sajedinia, according to the semiofficial Tasnim news agency. He later said police had removed the protesters from the building and arrested some of them, saying the situation had been "defused."

The cleric's execution could also complicate Saudi Arabia's relationship with the Shiite-led government in Iraq. The Saudi embassy in Baghdad reopened for the first time in nearly 25 years on Friday. Already on Saturday there were public calls for Prime Minister Haider al-Abadi to shut the embassy down again.

Al-Abadi tweeted Saturday night that he was "shocked and saddened" by al-Nimr's execution, adding that "peaceful opposition is a fundamental right. Repression does not last."

Hundreds of al-Nimr's supporters also protested in his hometown of al-Qatif in eastern Saudi Arabia, in neighboring Bahrain where police fired tear gas and bird shot, and as far away as northern India.

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Associated Press writers Jon Gambrell in Dubai, United Arab Emirates, and Joseph Krauss and Maamoun Youssef in Cairo contributed to this report.