Saudi Arabia said on Sunday it wanted to avert war in the region but stood ready to respond with “all strength” following last week’s attacks on Saudi oil assets, telling Iran that the ball was now in its court.

Riyadh has accused Tehran of ordering Tuesday’s drone strikes on two oil pumping stations in the kingdom, claimed by Yemen’s Iran-aligned Houthi group. Two days earlier, four vessels, including two Saudi oil tankers, were sabotaged off the coast of the United Arab Emirates.

In response, countries of the Gulf Cooperation Council (GCC) began “enhanced security patrols” in the international waters of the Arabian Gulf area on Saturday, the US Navy’s Bahrain-based Fifth Fleet said on Sunday.

Iran has denied involvement in either operation, which come as Washington and the Islamic Republic spar over sanctions and the US military presence in the region, raising concerns about a potential US-Iran conflict.

“The kingdom of Saudi Arabia does not want a war in the region nor does it seek that,” minister of state for foreign affairs Adel al-Jubeir told a news conference. “It will do what it can to prevent this war and at the same time it reaffirms that in the event the other side chooses war, the kingdom will respond with all force and determination, and it will defend itself and its interests.”

Saudi Arabia’s King Salman on Sunday invited Gulf and Arab leaders to convene emergency summits in Mecca on May 30 to discuss implications of the attacks.

“The current critical circumstances entail a unified Arab and Gulf stance toward the besetting challenges and risks,” the UAE foreign ministry said in a statement.

The US Navy’s Fifth Fleet said in its statement about increased maritime patrols that GCC countries were “specifically increasing communication and coordination with each other in support of regional naval cooperation and maritime security operations in the Arabian Gulf”, with navies and coast guards working with the US Navy.

Saudi Arabia’s Sunni Muslim ally the UAE has not blamed anyone for the tanker sabotage operation, pending an investigation. No-one has claimed responsibility, but two US government sources said last week that U.S. officials believed Iran had encouraged the Houthi group or Iraq-based Shi’ite militias to carry it out.

The drone strike on oil pumping stations, which Riyadh said did not disrupt output or exports, was claimed by the Houthis, who have been battling a Saudi-led military coalition in a war in Yemen since 2015.

The head of the Houthis’ Supreme Revolutionary Committee, Mohammed Ali al-Houthi, derided Riyadh’s call to convene Arab summits, saying in a Twitter post that they “only know how to support war and destruction”.

A Norwegian insurers’ report seen by Reuters said Iran’s Revolutionary Guards were “highly likely” to have facilitated the attack on vessels near the UAE’s Fujairah emirate, a main bunkering hub lying just outside the Strait of Hormuz.

Iranian foreign minister Javad Zarif has dismissed the possibility of war erupting, saying Tehran did not want conflict and no country had the “illusion it can confront Iran”. This stance was echoed by the head of Iran’s elite Revolutionary Guards on Sunday.

“We are not pursuing war but we are also not afraid of war,” Major General Hossein Salami was cited as saying by the semi-official news agency Tasnim.

Washington has tightened economic sanctions against Iran, trying to cut Tehran's oil exports to zero, and beefed up the US military presence in the Gulf in response to what it said were Iranian threats to US troops and interests.

Crown Prince Mohammed bin Salman discussed regional developments, including efforts to strengthen security and stability, in a phone call with US Secretary of State Mike Pompeo, the Saudi Media Ministry tweeted.