Saudi Arabia on Sunday came under attack globally a day after it carried out mass execution of 47 people, including Shia cleric Sheikh Nimr al-Nimr who was a vocal critic of the government and the Saudi monarchy.
The execution -- some beheaded, and others were shot by firing squad -- has provoked a huge backlash among the Shia community across the world and threatens to deepen the serious sectarian conflict in the Middle East.
Ironically, Saudi Arabia is the head of the United Nations human rights council.
Sheikh Nimr al-Nimr was a symbolic leader of Shia protesters during the Arab Spring uprisings in many parts of the Persian Gulf.
In Iranian capital Tehran, protesters threw petrol bombs and stormed the embassy. The kingdom's consulate in Mashhad, Iran's second biggest city in the country's northeast, was also set on fire.
Shia-dominated Iran has said that rival Saudi Arabia is going to pay a "high price" for the executions.
Iranian President Hassan Rouhani criticised Saudi Arabia for killing Nimr.
"I have no doubt that the Saudi government has damaged its image, more than before, among the countries in the world -- in particular (among) Islamic countries -- by this un-Islamic act," he said in a statement.
There has been a huge upsurge in executions in Saudi Arabia in 2015 with at least 157 people put to death as compared to 90 people who were executed in 2014.
Iran's supreme leader Ayatollah Ali Khamenei said that Saudi Arabia will face "divine revenge" for executing the top Shiite cleric.
Khamenei called the killing of Nimr "a political mistake by the Saudi government" which would "haunt its politicians".
"The unjustly spilt blood of this martyr will have quick consequences," Khamenei told clerics in the Iranian capital. "God will not forgive."
"This scholar neither encouraged people into armed action nor secretly conspired for plots but the only thing he did was utter public criticism rising from his religious zeal," he said of Nimr.
However, Saudi Arabia's foreign ministry, in a 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."
The country's interior ministry said the executed men had been convicted of adopting the radical "takfiri" ideology, joining "terrorist organizations" and implementing various "criminal plots."
Sunni Saudi Arabia and Shiite Iran have been locked in 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 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, there were public calls for Prime Minister Haider al-Abadi to shut the embassy down again.
The United Nations too came down hard upon Saudi Arabia for carrying out the executions.
"Under international human rights law, the death penalty may only be imposed, in countries that still have this form of punishment, if a strict set of substantive and procedural requirements are met," UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein said.
"The category of 'most serious crimes' for which the death penalty is still permissible, has been consistently interpreted by human rights mechanisms as being restricted to murder and other forms of intentional killing," he added.
"Convictions cannot be based on confessions obtained under torture and ill-treatment, or trial proceedings that fall short of international standards," the High Commissioner said.
The UN rights chief also said that convictions for applying the death penalty that fall short of international standards are "unconscionable" because "any miscarriage of justice as a result of capital punishment cannot be undone".
"Now we see almost one-third of the 2015 total executed in a single day," Zeid said, adding, "That is a very disturbing development indeed, particularly as some of those sentenced to death were accused of non-violent crimes."
He urged the government of Saudi Arabia to impose a moratorium on all executions and "to work with the UN and other partners on alternative strategies to combat terrorism".
The UN General Assembly has repeatedly passed a number of resolutions calling on member states who retain the death penalty to establish a moratorium on executions with a view to abolishing the death penalty altogether.
