Saudi Arabia has said it's cutting diplomatic ties with Iran, in the latest fallout to erupt after Riyadh’s execution of an opposition Shi'ite cleric prompted outraged protesters to storm the Saudi Embassy in Tehran.

Foreign Minister Adel al-Jubeir announced the decision to sever ties with Tehran on January 3, saying that all Iranian diplomats must leave Saudi Arabia within 48 hours.

The move came amid increasingly harsh rhetoric between Riyadh and Tehran, with Iran's supreme leader warning of "divine vengeance” for the execution of Sheikh Nimr al-Nimr. It also came almost a day after protesters stormed the Saudi Embassy in Tehran, setting fires and throwing papers from the roof.

Saudi Arabia, ruled by a Sunni-led royal dynasty, is engaged in a tug of war with Shi’ite-led Iran throughout the Middle East. Both sides have used proxy forces to struggle for or maintain influence in places like Yemen, as well as Bahrain, Iraq, and Syria.

The execution of Nimr, announced on January 2 by Saudi Arabia, was expected to fuel further outbreaks of proxy violence.

Nimr was a central figure in protests by Saudi Arabia's marginalized Shi'ite minority until his arrest in 2012 and later conviction on terrorism charges. His execution drew condemnation from Shi'a across the region.

In addition to Nimr, 46 others, including three Shi'ite dissidents and several Al-Qaeda militants, were put to death.

In Washington, a U.S. State Department spokesman warned that Nimr's execution could worsen sectarian strife at a time when tensions needed to be reduced.

A day after protesters stormed and looted part of the Saudi Embassy in Tehran, Iranian authorities said on January 3 that 44 demonstrators had been arrested, but hard-liners also called for another demonstration later in the day.

Supreme Leader Ayatollah Ali Khamenei said in a statement on January 3 that Nimr "neither invited people to take up arms nor hatched covert plots. The only thing he did was public criticism."

In a sign that Iranian authorities may be seeking to keep the reaction from spiraling out of control, Iranian President Hassan Rohani on January 3 condemned Nimr's execution but also denounced attacks on the Saudi Embassy and Consulate as "totally unjustifiable."

Rohani said that "the buildings should be legally and religiously protected in the Islamic Republic of Iran."

Sectarian Tensions

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

It accused Tehran of "blind sectarianism" and said that "by its defense of terrorist acts" Iran was a "partner in their crimes in the entire region."

Earlier, Iran's hard-line Revolutionary Guards had promised "harsh revenge" against the Saudi Sunni royal dynasty for his execution. 

Iran previously warned that executing the cleric would "cost Saudi Arabia dearly."

Ayatollah Ahmad Khatami, a member of the Assembly of Experts and a Friday Prayer leader, denounced the execution as a "crime" by Saudi Arabia's "infamous regime."

"This...blood will stain the collar of the House of Saud and wipe them from the pages of history," Khatami was quoted as saying on January 2.

Iran’s powerful Islamic Revolutionary Guards Corps (IRGC) said in a statement that the Saudi government would pay a "heavy price" for “this shameful act,” which it said was a sign of the “decay” of the Saudi rulers. 

“The criminal act of execution of Sheikh Nimr the leader of Shia in Saudi Arabia is part of a Zionist conspiracy to sow discord among the world Muslims which will be aborted by the Heavenly blessings coming down to us by the pure blood of these martyrs,” the statement published by Iranian media said.

In Iraq, whose Shi'ite-led government is close to Iran, prominent religious and political figures demanded that ties with Riyadh be severed.

Iraqi Prime Minister Haidar al-Abadi warned that Nimr’s execution would have repercussions on regional security.

He wrote on his verified Facebook account that muffling voices and executing opponents "would lead to nothing but more destruction," expressing "intense shock" upon hearing the news of the execution.

Former Prime Minister Nuri al-Maliki said Nimr's execution would "topple the Saudi regime". 

Iraqi lawmaker Muhammad al-Sayhud warned that Nimr's execution was intended to fuel sectarian strife in the region. 

"This measure taken by the ruling family [of Saudi Arabia] aims at reigniting the region, provoking sectarian fighting between Sunnis and Shi'a," he told Al-Sumaria TV.

Prominent Iraqi Shi'ite cleric Muqtada al-Sadr called for demonstrations in Persian Gulf countries and in Iraq to protest the execution of Nimr by Saudi Arabia.

"I ask that the Shi'a of Saudi Arabia...show courage in responding even through peaceful demonstrations, and the same for the Shi' in the Gulf, so as to deter injustice and government terrorism in the future," Sadr said on his website.

In Bahrain, police used tear gas against several dozen people protesting Nimr’s execution while carrying his pictures.

'Foreign Meddling'

Meanwhile, Nimr's brother said the family was shocked by news of the execution but hoped that any reaction would be peaceful:

"We hope that any reactions would be confined to a peaceful framework. No one should have any reaction outside this peaceful framework. Enough bloodshed," Muhammad al-Nimr told Reuters.

He said the cleric was found guilty of seeking "foreign meddling" in the kingdom, "disobeying" the country's rulers, and taking up arms against the security forces.

Nimr’s brother was later quoted as saying that Saudi authorities told the family that the cleric had already been buried without informing them at which cemetery. 

Hundreds of members of its Shi'ite minority were arrested after the protests during which several policemen were killed in shooting and firebomb attacks. 

The kingdom also detained thousands of militant Islamists after a series of Al-Qaeda attacks from 2003-06 that killed hundreds, and has convicted hundreds of them.

The ministry said the executions were carried out on January 2 in 12 different areas of the kingdom.

The executions are Saudi Arabia's first in 2016. At least 157 people were put to death last year, a big increase from the 90 people killed in 2014.

With reporting by Reuters, dpa, AFP, AP, the BBC, IRNA, Fars, and Mehr