RIYADH - The diplomatic crisis surrounding Saudi Arabia and Iran widened on Tuesday as Kuwait recalled its ambassador to Tehran in the face of growing international concern.

Joining Riyadh and its Sunni Arab allies in taking diplomatic action, Kuwait said it was withdrawing its envoy over a weekend attack on the Saudi embassy in Tehran.

Kuwait’s move came after the UN Security Council strongly condemned the attack, carried out by protesters angry over Saudi Arabia’s execution of a prominent Shiite cleric.

Tensions between Saudi Arabia, the main Sunni power, and Shiite-dominated Iran have erupted this week into a full-blown diplomatic crisis, sparking widespread worries of regional instability.

Iran lashed out again at Saudi Arabia for the execution on Tuesday, with President Hassan Rouhani accusing Riyadh of seeking to “cover its crime” by severing ties. “One does not respond to criticism by cutting off heads,” Rouhani said, referring to the usual Saudi practice of carrying out executions with beheading by the sword.

Washington and other Western powers have called for calm amid fears the dispute could raise sectarian tensions across the Middle East and derail efforts to resolve conflicts from Syria to Yemen. The Security Council joined those calls late on Monday, issuing a statement urging all sides to “take steps to reduce tensions in the region”.

The statement by the 15-member council condemned “in the strongest terms” the attacks which saw protesters firebomb the Saudi embassy in Tehran and its consulate in Iran’s second-biggest city Masshad. But the council made no mention of the event that set off the crisis - Saudi Arabia’s execution on Saturday of Sheikh Nimr al-Nimr, a cleric and activist whose death sparked widespread protests among Shiites. Saudi Arabia cut off diplomatic ties with Tehran in protest at the attacks on Sunday and has severed air links with Iran.

Some of its allies among Sunni Arab states followed suit, with Bahrain and Sudan breaking off ties and the United Arab Emirates downgrading relations on Monday. Kuwait said Tuesday the embassy attacks “represent a flagrant breach of international agreements and norms and a grave violation of Iran’s international commitments”. Rouhani has condemned the attacks and Tehran’s mission to the UN vowed in a letter to the Security Council to “take necessary measures to prevent the occurrence of similar incidents in the future”.

Iranian officials have brushed aside the dispute, with government spokesman Mohammad Bagher Nobakht saying Tuesday it “will have no impact on Iran’s national development”.

“It is Saudi Arabia that will suffer,” he said. The six-nation Gulf Cooperation Council (GCC) of Sunni Arab states said it would meet in Riyadh Saturday for talks on the embassy attacks, a day before the Arab League is due to hold an emergency meeting.

“Foreign ministers of the GCC States will hold an extraordinary meeting in Riyadh on Saturday ... to discuss the repercussions of the attack on the Embassy of Saudi Arabia in Tehran and the Saudi consulate in the Iranian city of Mashhad,” GCC Secretary-General Abdullatif bin Rashid Al Zayani said in an emailed statement. Regional powerhouse Turkey also expressed alarm at the crisis Tuesday, with Prime Minister Ahmet Davutoglu saying: “We expect all countries in the region to show common sense and take steps aimed at easing the tensions in the region.” He said Ankara was “ready to make any effort” to help resolve the crisis. Iran and Saudi Arabia are on opposing ends of a range of crucial Middle East issues, including the war in Syria - where Tehran backs President Bashar al-Assad’s regime and Riyadh supports rebel forces - and Yemen where a Saudi-led coalition is battling Shiite insurgents.

Despite the fears, Saudi Arabia’s ambassador to the United Nations, Abdallah al-Mouallimi, insisted the row would not have an impact on efforts to resolve regional conflicts. “From our side, it should have no effect because we will continue to work very hard to support the peace efforts in Syria and Yemen,” Mouallimi told reporters.

When asked what it would take for ties to be restored, Mouallimi told reporters: “Very simple - Iran to cease and desist from interfering in the internal affairs of other countries, including our own.”

He added, “If they do so, we will of course have normal relations with Iran. We are not natural-born enemies of Iran.” Saudi Foreign Minister Adel al-Jubeir told Reuters Riyadh would also halt air traffic and commercial relations between the rival powers.

Jubeir blamed Iran’s “aggressive policies” for the diplomatic action, alluding to years of tension.

The spike in tensions comes after Iran last year secured a historic nuclear deal with world powers led by the United States, sparking major concern in longtime US ally Riyadh.

Nimr, one of 47 men executed on Saturday, was a driving force behind 2011 anti-government protests in eastern Saudi Arabia.

He was arrested in 2012 after calling for two Saudi governorates to be separated from the kingdom. Riyadh’s interior ministry at the time described him as an “instigator of sedition”.

A man was shot dead in Saudi Arabia’s Eastern Province late on Sunday, and two Sunni mosques in Iraq’s Shi’ite-majority Hilla province were bombed in the fallout from the dispute between the Middle East’s top Sunni and Shi’ite powers.

But analysts said fears of a sectarian rupture across the Middle East were premature, and the break in Saudi-Iran relations could be more a symptom of existing strains than evidence of new ones.

“The downgrading of ties is not fundamentally a question of responding to executions and the storming of an embassy... (but rather) a function of a much deeper conflict between the two states,” said Julien Barnes-Dacey, senior policy fellow at the European Council on Foreign Relations.