Saudi Arabia on Wednesday sought to rally support among Islamic nations against arch-rival Iran, demanding “firmness” over attacks on Gulf oil facilities ahead of three summits as regional tensions soar.

Saudi Foreign Minister Ibrahim al-Assaf blasted Iranian “interference” in the region, just hours after United States National Security Advisor John Bolton said Tehran was almost certainly behind oil tanker attacks.

The tough stance comes on the eve of emergency Arab and Gulf summits called by US-ally Saudi Arabia to discuss the standoff and ways to isolate Tehran amid fears of a military escalation.

Know more: Iran tensions overshadow Makkah summits

“Tehran's support for Houthi rebels in Yemen is proof of Iranian interference in other nations' affairs and this is something that... Islamic countries should reject,” Assaf told a gathering of foreign ministers of the 57-member Organisation of Islamic Cooperation (OIC) in Jeddah city.

A representative of Iran attended the gathering of OIC, of which it is a member, an AFP reporter said. But Iranian Foreign Minister Javad Zarif was not present.

Assaf added that attacks on oil installations must be addressed with “firmness and determination”. Two Saudi oil tankers, among four vessels, were the targets of mysterious acts of sabotage off the United Arab Emirates (UAE) on May 12, and Yemeni rebels have stepped up drone attacks on the kingdom — one of which resulted in the temporary shutdown of a major oil pipeline.

'Evil desires for chaos'

The four ships 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. Bolton, however, declined to provide specific evidence for Iran's hand in the attacks.

Iran strongly rejected the accusation. “Making such laughable claims... is not strange” coming from the US, Iranian foreign ministry spokesman Abbas Mousavi said.

“Bolton and other warmongers and chaos seekers should know that the strategic patience, high vigilance and complete defensive readiness of the Islamic Republic of Iran... will prevent the fulfillment of their evil desires for chaos in the region,” Mousavi added.

US experts are part of a five-nation team that is investigating the attacks off the UAE emirate of Fujairah. The new war of words 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 said that additional US forces were sent to the Middle East as a “deterrent” and that Washington's response will be prudent.

Rallying against Tehran

Regional tensions have spiked 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.

The Trump administration has ordered non-essential diplomatic staff out of Iraq, citing threats from Iranian-backed Iraqi armed groups. 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”.

Bolton said Washington wants to prevent the Islamic republic from producing nuclear weapons, downplaying differences in the US administration on the issue.

“There's no mistake here,” he said.

“That we all have the same objective of keeping Iran from getting deliverable nuclear weapons.” In an apparent bid to present a unified front against Tehran, Saudi Arabia is hosting Islamic, Arab and Gulf summits at the weekend in Makkah, Islam's holiest city.

Qatar's Sheikh Abdullah bin Nasser al-Thani will attend talks in Makkah, its foreign ministry said on Wednesday, one of the first high-level contacts following a two-year Riyadh-led boycott of Doha.

Since June 2017, Saudi Arabia along with the UAE and their allies have enforced a boycott of Qatar including bans on shipping, trade, direct flights, overflight and land crossings.

The alliance, which also includes Bahrain and Egypt, accuses Doha of supporting Islamic movements and backing Iran — claims Qatar rejects.