Saudi Arabia's King Salman on Thursday urged Gulf Arab states to work together to confront what he called Iran's "criminal" actions in the region.

"The Iranian regime's interference in the internal affairs of the countries of the region, development of nuclear and missile programs, and its threats to freedom of international shipping are a threat to global oil supply," the king told an emergency summit in the holy city of Makkah.

Its "recent criminal acts... require that all of us work seriously to preserve the security... of GCC (Gulf Cooperation Council) countries," the king added, referring to recent attacks on Gulf oil installations.

His comment came a day after hawkish 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 strongly rejected the accusation.

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, is hosting leaders from across the Arab and Muslim world for emergency Gulf and Arab summits and a meeting of heads of state from Islamic nations.

Riyadh called the talks to discuss the standoff with Iran and ways of isolating Tehran amid fears of a military confrontation.