Iran denied on Sunday it was involved in Yemen rebel drone attacks the previous day targeting the world’s biggest oil processing facility and an oil field in Saudi Arabia, just hours after America’s top diplomat alleged that Tehran was behind the “unprecedented attack on the world’s energy supply”.The attacks on Saturday, claimed by Yemen’s Houthi rebels, resulted in “the temporary suspension of production operations” at the Abqaiq processing facility and the Khurais oil field, Riyadh said.That led to the interruption of an estimated 5.7 million barrels in crude supplies, authorities said while pledging the kingdom’s stockpiles would make up the difference. While markets remain closed on Sunday, the attack could shock world energy prices. They also increased overall tensions in the region amid an escalating crisis between the United States and Iran over Tehran’s unravelling nuclear deal with world powers.Late on Saturday, US Secretary of State Mike Pompeo directly blamed Iran for the attack on Twitter, without offering evidence to support his claim. The US, Western nations, their Gulf Arab allies and United Nations experts allege Iran supplies the Houthis with weapons and drones — a charge that Tehran denies. Iranian Foreign Ministry spokesman Abbas Mousavi dismissed Pompeo’s remarks as “blind and futile comments”.“The Americans adopted the ‘maximum pressure’ policy against Iran, which, due to its failure, is leaning towards ‘maximum lies’,” Mousavi said in a statement.First word of Saturday’s assault came in online videos of giant fires at the Abqaiq facility, some 330 kilometres northeast of the Saudi capital, Riyadh.Machine-gun fire could be heard in several clips alongside the day’s first Muslim call to prayers, suggesting security forces tried to bring down the drones just before dawn. In daylight, Saudi state television aired a segment with its local correspondent near a police checkpoint, a thick plume of smoke visible behind him.US President Donald Trump called Saudi Arabia’s Crown Prince Mohammed bin Salman to offer his support for the kingdom’s defence, the White House said. The crown prince assured Trump that Saudi Arabia is “willing and able to confront and deal with this terrorist aggression”, according to a news release from the Saudi Embassy in Washington.Saudi Aramco describes its Abqaiq oil processing facility in Buqyaq as “the largest crude oil stabilisation plant in the world”. The facility processes sour crude oil into sweet crude, then transports it onto transshipment points on the Persian Gulf and the Red Sea or to refineries for local production. Estimates suggest it can process up to 7m barrels of crude oil a day. By comparison, Saudi Arabia produced 9.65m barrels of crude oil a day in July.The Khurais oil field is believed to produce over 1m barrels of crude oil a day. It has estimated reserves of over 20 billion barrels of oil, according to Aramco.There was no immediate impact on global oil prices as markets were closed for the weekend. Benchmark Brent crude had been trading at just above $60 a barrel.