Saudi Arabia’s King Salman has said that attacks on Saudi oil assets last month are a threat to global oil supplies and regional security, while again accusing Iran-backed groups of carrying them out.

“The drone attacks on Saudi oil pumping stations carried out by groups supported by Iran not only threaten the security of the kingdom and the Gulf, but also threaten maritime safety and global oil supplies,” Salman said at an Organisation of Islamic Cooperation summit in the Saudi city of Mecca on Saturday.

On Friday Salman convened emergency summits of Gulf and then Arab leaders to discuss drone strikes on oil installations in Saudi and attacks on four vessels, including two Saudi oil tankers, off the UAE coast in May. Salman told the Arab meeting that decisive action was needed to stop Iranian “escalations” in the region.

Riyadh has accused Tehran of ordering the drone strikes, which were claimed by Yemen’s Iran-aligned Houthi group. US national security adviser John Bolton said on Thursday that evidence of Iran’s being behind the tanker attacks would be presented to the UN Security Council as early as next week.

Tehran has denied involvement in either attack.

Salman said the summit would seek to confront “aggressive threats and subversive activities” and work for the future of Arab and Islamic states.

Notably absent from the 57-member summit was Turkey’s President Recep Tayyip Erdogan. The regional heavyweight was instead represented by its foreign minister Mevlut Cavusoglu.

Erdogan’s visit would have been his first to the kingdom since the brutal murder last October of journalist Jamal Khashoggi in the Saudi consulate in Istanbul, which tarnished the international reputation of Crown Prince Mohammed bin Salman.

The OIC meeting is the third and final summit hosted by Saudi Arabia this week.

Salman also said the Palestinian cause represented a core issue for the OIC and that the kingdom “refused any measures that touch on the historical and legal position of East Jerusalem”.