The holy city of Mecca prepared to welcome Arab and Muslim leaders Thursday for three summits, as Saudi Arabia seeks to rally support against arch-rival Iran over attacks on oil installations.
The call came just hours after US National Security Advisor John Bolton said Iran was almost certainly behind the sabotage of four ships, including two Saudi oil tankers, off the UAE coast.
Iran-aligned Yemeni rebels meanwhile have stepped up drone attacks on the kingdom -- one of which resulted in the temporary shutdown of a major oil pipeline.
Saudi Arabia, a staunch US ally, was getting ready to welcome leaders from across the Arab and Muslim world for emergency Gulf and Arab summits and a meeting of the heads of state of Islamic nations.
Riyadh called the talks to discuss the standoff with Iran and ways to isolate Tehran amid fears of a military confrontation.
"Tehran's support for Huthi rebels in Yemen is proof of Iranian interference in other nations' affairs and this is something that... Islamic countries should reject," Saudi Foreign Minister Ibrahim al-Assaf told a gathering of foreign ministers of the 57-member Organization of Islamic Cooperation (OIC) in western Jeddah city overnight Thursday.
Contrary to expectations, an Iranian delegation headed by Reza Najafi, director general for international peace and security affairs at Iran's foreign ministry, represented the Islamic republic at the meeting.
Assaf said that attacks on oil installations must be addressed with "firmness and determination".
Tensions in the region spiked after the four ships were damaged in a sabotage attack off the coast of the emirate of Fujairah on May 12.
The vessels were attacked using "naval mines almost certainly from Iran", Bolton told a press conference in Abu Dhabi on Wednesday.
"There's no doubt in anybody's mind in Washington who's responsible for this," he said in a clear reference to Iran. Iran strongly rejected the accusation.
"Making such laughable claims... is not strange" coming from the US, foreign ministry spokesman Abbas Mousavi said. US experts are part of a five-nation team that is investigating the ship attacks.
The new war of words between Tehran and Washington follows a US military buildup that includes the deployment of an aircraft carrier, B-52 bombers and 1,500 more troops to the region.
Bolton however said that additional US forces were sent to the Middle East as a "deterrent" and that Washington's response will be prudent.
Regional tensions have grown since US President Donald Trump's administration reimposed sanctions against Iran after Washington unilaterally pulled out of a multilateral 2015 nuclear accord signed with the Islamic republic.
But Trump appeared to soften his hawkish tone towards Tehran, saying during a visit to Japan on Monday that his government does not seek "regime change".
Saudi Arabia is hosting the three summits in an apparent bid to present a unified front against Tehran.
Qatar will be represented by its Prime Minister Sheikh Abdullah bin Nasser al-Thani, the highest ranking official to visit the kingdom since the start of a two-year-old Saudi-led boycott.
Saudi Arabia, the UAE, Bahrain and Egypt have enforced the economic and diplomatic boycott of Qatar since June 2017, including bans on shipping, trade, direct flights, overflight and land crossings.
The alliance accuses Doha of supporting Islamist movements and backing Iran -- claims Qatar rejects.
Large banners and flags decorated the streets of Mecca, Islam's holiest city, to welcome the leaders.
The summits coincide with the last few days of the Muslim fasting month of Ramadan when Mecca throngs with hundreds of thousands of pilgrims.
The summits are held at midnight as Muslims break their day-long fasting at sunset and then go into several hours of special prayers known as Taraweeh.
Drapped in seamless all-white uniforms, worshippers walked under lampposts decorated with flags of participating nations while heading to the Grand Mosque to perform Umrah or minor pilgrimage.
The large crowds could pose a logistic headache for the organisers who sealed off six major roads for leaders and advised pilgrims to use alternative streets.
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