Diplomatic tensions between Saudi Arabia and Iran began with the kingdom's execution of 47 people convicted of terrorism charges - including a prominent Shia cleric - and later saw attacks on Saudi diplomatic posts in the Islamic Republic.
Some nations have followed the Saudis' lead in severing or downgrading ties with Iran, while others have offered words of caution aimed at cooling the war of words before it escalates further.
Here is a look at where countries stand:
THE MAIN ACTORS:
Saudi Arabia - The kingdom severed ties to Iran after attacks on two of its diplomatic missions following its execution of a Shia cleric last weekend; it also later cancelled all flights between the two nations.
Iran - Since the attack on the diplomatic posts, Iran says it has made arrests and has criticised the violent protesters. However on Tuesday, President Hassan Rouhani took a slightly harder line, saying Saudi Arabia's move to sever ties with his country could not "cover its crime" of executing Nimr.
COUNTRIES BACKING SAUDI ARABIA:
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Bahrain - The tiny, Shia-majority island kingdom off the Saudi coast - which long has relied on Saudi Arabia for support of its Sunni rulers - was the first to cut ties with Iran. Bahraini officials repeatedly have accused Iran of training fighters and attempting to smuggle arms into the country, which hosts the US Navy's 5th Fleet.
Sudan - The African nation cut its diplomatic ties to Iran and gave Iranian diplomats two weeks to leave the country. Sudan once tilted towards Iran, but has been looking to Saudi Arabia for aid since the secession of oil-rich South Sudan in 2011.
United Arab Emirates - The oil-rich country of seven emirates says it will reduce the number of diplomats in Iran, recall its ambassador and focus only on business relations. While backing Saudi Arabia, it may have chosen to reduce - rather than completely sever ties - because of a long trading history with Iran.
Kuwait - The oil-rich country is recalling its ambassador from Tehran, but it is not immediately clear how Kuwaiti-Iranian diplomatic ties will be affected. Tiny Kuwait is home to both Shia and Sunnis living in peace and has the most free-wheeling political system among all Gulf nations.
OMAN - The sultanate has long historical ties to Iran and served as the base for secret talks between Iranian and US officials that jump-started the deal reached between Iran and world powers over the Islamic Republic's contested nuclear programme.
THOSE BACKING IRAN:
Lebanese Hezbollah Movement - Hezbollah was founded in 1982 with the help of Iran's Revolutionary Guards after Israel invaded Lebanon. The group is one the main Iran-backed factions in the region.
Syria's embattled President Bashar al-Assad - Iran has been one of the biggest supporters of Syria since the 1980s and has stood by Assad's government in his country's grinding civil war. Saudi Arabia has been one of the biggest benefactors of those trying to overthrow him.
OTHER REGIONAL ACTORS:
Israel - Israel considers Iran to be its greatest regional threat because of its nuclear programme, its arsenal of long-range missiles, its support of anti-Israel armed groups, and its repeated threats to destroy it. While Israel has no direct ties to Saudi Arabia either, the countries have come closer because of a shared concern over Iran's growing influence.
The Palestinians- The Palestinian Authority issued a statement after the execution of Nimr saying it stands alongside the Saudis in their fight against "terrorism". The Saudis are the largest donor to the Palestinian Authority in the Arab world, providing them some $200 million annually. The Palestinian Authority, and the Fatah faction that leads it, has had a strained relationship with Iran because of its support of its rival, Hamas.
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Yemen - The Arab world's poorest country is torn by a civil war pitting its internationally recognised government, backed by a Saudi-led coalition, against Shia rebels known as Houthis, who are supported by Iran.
THOSE URGING CAUTION:
The United Nations - UN Secretary-General Ban Ki-moon has urged Saudi Arabia and Iran to support peace efforts in Syria and Yemen and avoid escalating tensions.
European Union - The 28-nation bloc, which opposes the death penalty, criticised Saudi Arabia's mass executions and said Nimr's case undermined freedom of expression and basic political rights in the kingdom. Since tensions flared between Iran and Saudi Arabia, the EU foreign policy chief has had phone contact with both sides, fearing an escalation would further destabilise the whole region.
The United States - The White House has urged Saudi Arabia and Iran to not let their dispute derail efforts to end the Syrian civil war, while President Barack Obama's administration also hopes to see the Iranian nuclear deal through.
United Kingdom - Britain and Iran reopened their respective embassies in 2015, four years after hard-line protesters stormed the British embassy in Tehran. Saudi Arabia is a key diplomatic and economic ally of Britain, though Middle East Minister Tobias Ellwood said Britain told the kingdom about its "disappointment at the mass executions".