TEHRAN: Iranian protesters set fire to the Saudi Embassy during a demonstration against the execution of prominent Shiite cleric Nimr Al-Nimr by Saudi authorities on Saturday. - AFP

TEHRAN: Iran's supreme leader warned yesterday that Saudi Arabia would face "divine revenge" for deciding to execute a Shiite cleric, calling the killing a mistake which would "haunt" the kingdom. Ayatollah Ali Khamenei was joined in his condemnation of Nimr Al-Nimr's death by neighboring Iraq's top Shiite authority, Grand Ayatollah Ali Al-Sistani, who described the death sentence as an unjust act of aggression.

Their comments came as protests in Iran yesterday spread to Bahrain, Pakistan, Indian Kashmir and Lebanon a day after a mob set fire to the Saudi embassy in Tehran and ransacked it before dozens were arrested. The Saudi consulate in Mashhad, Iran's second city, was also set on fire. The demonstrations highlighted fury over the killing of Nimr, a Saudi Shiite who spent more than a decade studying theology at Iran's seminaries. On top of the ongoing wars in Syria and Yemen, Nimr's execution set the Middle East's main Shiite countries further apart from their Sunni counterpart in Riyadh.

While Shiite leaders hit out at Saudi Arabia, Kuwait, United Arab Emirates and Bahrain defended their ally, saying the executions were necessary to confront extremism. An official source at the Kuwaiti Foreign Ministry said yesterday Kuwait sharply condemned attacks by Iranian demonstrators on the Saudi embassy in Tehran and the Saudi consulate in Mashhad. Iranian authorities should shoulder responsibility for protecting the embassy and ensuring the safety of its staff, the source requested.

Such attacks are a flagrant violation of Vienna Convention that requires states to protect and safeguard diplomatic missions and to ensure the safety of their staff, the source reminded. The source called on Iranian authorities to abide by all international rules and norms which state the respect of states' sovereignty and non-interference in their internal affairs. In addition, the source reiterated Kuwait's support to all measures adopted by Saudi Arabia to maintain its security and stability.

The Gulf Cooperation Council (GCC) also condemned the "barbaric' aggression on the Saudi missions, holding the Iranian authorities fully responsible for these "acts of terrorism". GCC Secretary-General Abdullatif Al-Zayani also denounced Iran's "hostile and fomenting" statements against Saudi Arabia after the kingdom carried out "legitimate rulings against terrorists". He considered the statements "blatant interference in the kingdom's internal affairs." He reiterated the GCC's support to the resolutions the kingdom had made to "fight all forms of terrorism and track perpetrators of acts of terrorism and agitators and bring them to justice".

Nimr, 56, was a force behind anti-government protests in eastern Saudi Arabia in 2011. He was executed Saturday along with 46 Shiite activists and Sunnis who the Saudi interior ministry said were involved in Al-Qaeda killings. Some were beheaded, others were shot by firing squad. Nimr's brother, Mohammed, said he had been told the corpse would not be returned to the family and had been buried "in a cemetery of Muslims".

Khamenei, in a speech to clerics in Tehran, said the killing would not go unanswered. "The unjustly spilt blood of this martyr will have quick consequences," he said. "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." Sistani's remarks were not as strong as Khamenei's but in a statement he alluded to repercussions. "The spilling of their pure blood - including of the late cleric Sheikh Nimr Al-Nimr, may his soul rest in peace - is an injustice and an aggression," he said.

Nimr was arrested in 2012, three years after calling for the oil-rich Eastern Province's Shiite-populated Qatif and Al-Ihsaa governorates to be separated from Saudi Arabia and united with Bahrain. Shiites there complain of marginalization. But the Saudi interior ministry described him at the time of his arrest as an "instigator of sedition". A video on YouTube in 2012 showed Nimr making a speech celebrating the death of then-interior minister Prince Nayef bin Abdulaziz.

Demonstrations outside the Saudi embassy and at Palestine Square in Tehran attracted around 1,500 people yesterday. Activists erected a street sign bearing Nimr's name outside the kingdom's embassy, but state media said the change had not been approved. Iran's President Hassan Rouhani had earlier intervened to distance the government from Saturday's violence at both the embassy and the consulate.

He called such demonstrators radicals and while deploring Nimr's killing said criminality at the diplomatic buildings was "totally unjustifiable". Forty-four people were arrested, prosecutors said. Several small protests took place in Baghdad and elsewhere in Iraq, including in the southern town of Nasiriyah yesterday.

The United States and European Union have expressed alarm at the executions, with Washington warning that Riyadh risked "exacerbating sectarian tensions at a time when they urgently need to be reduced". UN Secretary General Ban Ki-moon said he was "deeply dismayed" by the state-sanctioned killings. France and Germany condemned the executions, voicing concerns about growing tensions in the Middle East.

Saudi Arabia's interior ministry said the executed men were convicted of adopting the radical "takfiri" ideology, joining "terrorist organizations" and implementing various "criminal plots". An official list included Sunnis convicted of involvement in Al-Qaeda attacks that killed dozens - Saudis and foreigners - in 2003 and 2004. Among them was Fares Al-Shuwail, described by Saudi media as Al-Qaeda's top religious leader in the kingdom.

Hassan Nasrallah, leader of Lebanon's Shiite movement Hezbollah, said Saudi Arabia had a "criminal and terrorist" government whose rulers wanted to spark "a conflict between Sunni and Shiite" Muslims. Executions have soared in Saudi Arabia since King Salman ascended the throne a year ago with 153 people put to death in 2015, nearly twice as many as in 2014. - Agencies