The cold war between Saudi Arabia and Iran turned a lot hotter in the past 48 hours, after the Saudis executed a Shiite cleric accused of terrorism on Saturday and hours later an Iranian mob ransacked and fire-bombed the Saudi embassy in Tehran.
By Sunday, Riyadh escalated tensions further by cutting diplomatic ties with Tehran. In a news conference, the Saudi Minister of Foreign Affairs, Adel al-Jubeir gave Iranian diplomats 48 hours to leave the country.
"The continued attacks on diplomatic missions is a flagrant violation of all international treaties," said the foreign minister. He also accused Tehran of backing terrorism.
The diplomatic break hardens the bitter rivalry between two capitals in a race for regional influence.
The two powers reflect the deep sectarian divide in the region, which has grown to fever pitch as Saudi Arabia, the regional Sunni power, and Shiite Iran support opposing sides in wars in Yemen and Syria.
The strains have also escalated since the U.S. and five world powers signed a nuclear deal with Tehran.
Despite the tensions, Saudi Arabia and Iran had also maintained diplomatic relations — until Sunday.
"Now, the Saudis can cut off relations. They can be the aggrieved party," says Mohamad Bazzi, a professor at New York University who is writing a book on the Saudi/Iran proxy wars in the region. The attack on the Saudi embassy in Tehran was "in many ways a gift," he says referring to the mob that set the embassy alight in Tehran. Quickly, Saudi Arabia upped the ante in what seems like an attempt to shift condemnation away from the executions and to focus it on Iran.
The move comes after international criticism for the mass executions of 47 men in 12 cities across Saudi Arabia. Most of the executed were convicted of carrying out attacks on behalf of Al Qaeda more than a decade ago. In the sectarian landscape of the region, these men were all Sunni Muslims.
However, the most prominent of those executed is 56-year-old Nimr al Nimr, a Saudi citizen and a fiery Shiite cleric who had been an outspoken critic of the Saudi monarchy. He was convicted on terrorism charges, accused of shooting police officers during protests in the Kingdom's eastern province in 2011. But Nimr's defenders say his anti-government protest was non-violent and he said in interviews "the roar of the word is more powerful than bullets."
Nimr was condemned to death in in a closed trial that was widely criticized by human rights groups. His case was championed by UN chief Ban Ki Moon, and by Tehran, where top officials warned that Nimr's death would "cost Saudi Arabia dearly."
In interviews last month in Riyadh, Western diplomats were convinced the Saudis would grant Nimr clemency, and as one diplomat said, "the Saudis say that keeping quiet is the best guarantee of stability."
The executions came as a surprise to many in Saudi, but the Saudi leadership was well aware of likely turbulent reactions.
"There are two motivations," says one Gulf analyst who agreed to speak on condition of anonymity because of the sensitivity of the issues.
"One is to look tough on law and order by executing the Al Qaeda-linked prisoners," he says. Carrying out the death sentence on Nimr sends a strong message to Saudi Arabia's aggrieved Shiite minority that Iran has no say in internal Saudi decisions and domestic dissent has limits.
"There is also a calculation," says the analyst, "the Saudis want to consolidate their alliances in the region — that would lead to a stark choice between the two sides."
The reactions to the executions played out along sectarian lines. Shiite Iranians led the charge. The country's supreme leader posted on his website an illustration comparing Saudi rulers to the militants of ISIS. Sectarian protests also kicked off in Iraq and Lebanon.
At the same time Saudi Arabia's Sunni allies backed Riyadh. A top official in the UAE called the Saudi actions "a clear message against terrorism." In Egypt, a statement from Al-Azhar, the highest Sunni religious authority in the country, asserted, "Saudi Arabia has applied the law of God."
As a more toxic sectarian confrontation engulfs the region, the losers are likely to be Syria and Yemen. Most regional analysts say the solution to these devastating proxy wars can only be resolved when there is some accommodation between Riyadh and Tehran.
The latest dispute is a dangerous shift in a volatile region.