In the words of President Donald Trump, the US is prepared to retaliate for the drone strikes on the Saudi oil facility Abkaik and the Churais oil field. There is "reason to believe that we know who the author is," wrote Trump on Twitter. The United States stood gun on foot, but still waiting for confirmation and information from the kingdom on the cause of the attacks - and "under what conditions we should proceed". All options - including a military response - were on the table, a government official said.

The US government blamed Iran for attacking the largest oil refinery in Saudi Arabia. Foreign Minister Mike Pompeo wrote on Twitter: "Amid calls for de-escalation, Iran has now committed an unprecedented attack on world energy supply, with no evidence that the attacks came from Yemen."

The Shiite Houthi rebels in Yemen were already aware of the attack with ten drones and further attacks were announced. "We promise the Saudi regime that our next operation will be bigger and more painful," said Hothis military spokesman Jahia Saria.

The events in the kingdom cut Saudi oil production by half. Daily production fell by an estimated 5.7 million barrels of crude oil, equivalent to more than five percent of world supply. The attacks also hit oil prices. At the Mercantile Exchange New York futures exchange, US crude oil price rose $ 5.61 a barrel on Monday morning, or 10.2 percent, to $ 60.46. The price of the Brent variety climbed $ 7.84 a barrel or 13 percent to $ 68.06 a barrel.