Saudi Arabia has severed relations with Iran amid the furor that erupted over the execution by the Saudi authorities of a prominent Shiite cleric.
Foreign Minister Adel al-Jubair told reporters in Riyadh that the Iranian ambassador in Tehran had been given 48 hours to leave the country, citing concerns that Tehran's Shiite government was undermining the security of the Sunni kingdom.
Saudi Arabian diplomats had already departed Iran after angry mobs trashed and burned the Saudi embassy in Tehran overnight Saturday, in response to the execution of Sheikh Nimr Baqr al-Nimr earlier in the day.
Iran's supreme leader warned on Sunday that there would be divine retribution for Saudi Arabia's rulers after the execution of a renowned Shiite cleric, sustaining the soaring regional tensions that erupted in the wake of the killing.
The warning came hours after crowds of protesters stormed and torched the Saudi embassy in Tehran to vent their anger at the execution of Nimr Baqr al-Nimr, who was among 47 people put to death in the kingdom on Saturday.
In a posting on his website, Ayatollah Ali Khamenei warned that the execution "will cause serious troubles for the politicians of this [Saudi] regime in a very short time....The hands of divine vengeance will surely snatch - by their necks - those cruel individuals who took his life."
The execution of Nimr, an outspoken critic of the Saudi royal family, has ignited sectarian tensions across the already inflamed region and jeopardized U.S. diplomacy aimed at tamping down conflicts in the Middle East.
Most of the 47 executed on Saturday were Sunnis accused of participating in al-Qaida attacks. According to Saudi Arabia's Interior Ministry, some were beheaded and others were shot by firing squad in 12 different locations around the kingdom.
Nimr, however, was one of four Shiites put to death for political activism and the leading figure in the anti-government demonstrations that swept the mostly Shiite east of the country in 2011, inspired by the Arab Spring protests elsewhere in the region.
A photo montage also posted on Khamenei's website showed a split image of an Islamic State fighter preparing to carry out a beheading and a Saudi executioner. The caption asks the question "Any difference?" The photograph echoed numerous Iranian accusations that Saudi Arabia supports the Islamic State.
In response, Saudi Arabia issued an angry statement pointing out that Iran is often accused by many countries of supporting terrorism.
Iran "is the last regime in the world that could accuse others of supporting terrorism, considering that [Iran] is a state that sponsors terror, and is condemned by the United Nations and many countries," said a Foreign Ministry statement carried by the official Saudi news agency.
The Saudi statement also pointed out that Iran also is frequently criticized by the international community for carrying out large numbers of executions.
Iran carried out 694 executions in the first half of last year, according to an Amnesty International statement in July. Saudi Arabia, with a population nearly a third smaller than Iran's, carried out 157 in 2015, according to Amnesty and media reports.
The authorities in Tehran announced that they had made a number of arrests in connection with the rampage at the Saudi embassy in Tehran, and the Foreign Ministry pledged to secure Saudi Arabian diplomatic facilities against further attack.
"The diplomatic police are responsible for confronting any aggression against the diplomatic sites of Saudi Arabia and will act according to its duties to maintain public order and restore security to such places," Foreign Ministry spokesman Hossein Jaber Ansari said.
The Saudi consulate in the Iranian city of Mashad was also set on fire during the protests that erupted after Nimr's execution was announced.
The death sentence was carried out despite international appeals for clemency and repeated warnings from the kingdom's archenemy in the region, Iran, that there would be consequences if the popular cleric were killed.
The State Department, which had refrained from publicly joining the appeals for Nimr's life, said it had raised concerns at the highest levels of the Saudi government about the judicial process. In a statement, it called on Saudi Arabia "to respect and protect human rights" and to permit "peaceful expression of dissent."
"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 State Department said in a statement. "In this context, we reiterate the need for leaders throughout the region to redouble efforts aimed at de-escalating regional tensions."
Shiites around the world expressed outrage, potentially complicating a surge of U.S. diplomacy aimed at bringing peace to the region, according to Toby Matthiesen, an expert on Saudi Arabia at the University of Oxford.
Saudi Arabia and Iran are backing rival sides in Syria's war, and their enmity risks derailing a diplomatic effort led by the United States and Russia to convene peace talks between the factions in Geneva this month.
The two feuding powers also support opposing sides in the war in Yemen and more broadly find themselves in opposition in the deeply divided politics of the mixed Sunni-Shiite nations of Iraq and Lebanon.
Who was Nimr al-Nimr, why does his death matter?
Q: Who was Nimr al-Nimr?
Nimr al-Nimr, 57, a Shiite cleric from Saudi's oil-rich Eastern Province, was a well-known figure at anti-government demonstrations and criticized Saudi rulers in some of his sermons for their treatment of the kingdom's Shiite minority.
In 2009, he threatened to lead Saudi Arabia's Shiite Muslims to secession, provoking a government crackdown in the minority's eastern heartland. In his sermons, al-Nimr was critical of Sunni and Shiite autocratic rulers alike, though he reserved some of his most scathing attacks to the Saudi and Bahraini royal families.
In a meeting with U.S. diplomats in 2008, al-Nimr sought to distance himself from Tehran, according to a cable released by WikiLeaks. Iran, like other countries, acts out of self- interest, and Saudi Shiites shouldn't expect Iranian support based on sectarian unity, he said. The report describes him as a "second-tier political player" in the Eastern Province.
He was arrested in 2012, a year after popular uprisings swept parts of the Middle East, and sentenced to death in 2014.
Q: Why does his execution matter?
While Sunni-majority Saudi Arabia largely escaped the unrest that spread across the Arab world in 2011, the country's Shiites, who say they suffer discrimination, have occasionally protested and clashed with security forces. Most Saudi Shiites live near some of the world's largest oil fields in the eastern region, and according to the CIA World Factbook, make up between 10 percent and 15 percent of Saudi Arabia's population.
The execution "institutionalizes tension in Saudi Arabia by creating a symbol for Shiite grievances," Ibrahim Fraihat, senior foreign policy fellow at the Brookings Doha Center, said in an interview. "Not many people in the past saw him as the representative of the Shiite community, but now he has become one of the symbols of the tension between Shiite and Sunnis."
In 2015, Islamic State militants took advantage of the Saudi sectarian fault-lines and struck Shiite mosques in the Eastern Province.
Shiites are a majority in neighboring Bahrain, a small island that's home to the U.S. Fifth Fleet. Bahraini authorities regularly accuse Iran of supporting extremist Shiite groups, a charge the Islamic Republic denies. Hours after al-Nimr's death, scores of his supporters there took to the streets in protest, Agence France-Presse reported.
Q: Why carry out the execution given regional tensions?
Given the complex dynamics in the region in Yemen, Syria and Iraq, al-Nimr's execution was an illustration of Saudi Arabia's "get tough" policy against Iran and internal dissent, said Scott Lucas, an Iran analyst and professor of international politics at Birmingham University in Britain.
"The Saudis deliberately crossed the line by executing him, and to add insult to injury they used the rhetoric that lumps him in with al-Qaeda terrorists," he said.
Q: How did Iran react?
Iranian protesters armed with rocks and firebombs massed outside the Saudi embassy in Tehran late Saturday and set parts of the building on fire. A small group stormed the premises, ransacking offices, and several were arrested, Tehran police chief Hossein Sajedinia told the state-run Islamic Students' News Agency.
On Sunday, Iran's Supreme Leader Ayatollah Ali Khamenei said Saudi rulers will face "the divine hand of revenge" for their actions. Khamenei, the country's highest authority and a regular critics of Saudi policies, stopped short of saying Iran would take action.
Iranian President Hassan Rouhani, meanwhile, suggested he didn't seek to escalate the confrontation. While he denounced the execution, he condemned the attack on the Saudi embassy as unjustifiable.
This incident might "spiral quickly into domestic fight" in Iran between hardline and more moderate factions close to Rouhani, Lucas said.
Q: Will tensions between Iran and Saudi escalate further?
The ball is in the Iranian court. If we see any signal of asymmetrical warfare from the Iranians, any escalation in Iranian support for Houthis in Yemen, anything that appears to be a step-up of Hezbollah activity, which appears to be targeting Saudi in any way," Lucas said. "But I don't think it's going to happen."
At least one commentator, London-based Lebanese political satirist Karl Sharro, looks for tensions to simmer, not boil over, for now. Saudi Arabia and Iran are "like two guys in a bar shouting at each other for a long time, but not quite ready to take it outside just yet," he tweeted on Sunday.
---Vivian Nereim and Mohammed Aly Sergie contributed.