Iran denied on Sunday it was involved in Yemen rebel drone attacks the previous day that hit the world’s biggest oil processing facility and an oilfield in Saudi Arabia, just hours after the United States’s top diplomat alleged Tehran was behind the “unprecedented attack on the world’s energy supply.”

The attacks Saturday claimed by Yemen’s Houthi rebels resulted in “the temporary suspension of production operations” at the Abqaiq processing facility and the Khurais oilfield, 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.The amount Saudi Arabia is cutting back is equivalent to over five per cent of the world’s daily production.

While markets remained closed Sunday, the attack could shock world energy prices. They also increased overall tensions in the region amid an escalating crisis between the U.S. and Iran over Tehran’s unraveling nuclear deal with world powers.

Late Saturday, U.S. Secretary of State Mike Pompeo took to Twitter to directly blamed Iran for the attack, without offering evidence to support his claim.

“Amid all the calls for de-escalation, Iran has now launched an unprecedented attack on the world’s energy supply,” Pompeo wrote. “There is no evidence the attacks came from Yemen.”

The U.S., Western nations, their Gulf Arab allies and UN experts say Iran supplies the Houthis with weapons and drones, a charge that Tehran denies.

A satellite image provided by NASA Worldview shows fires following the attacks in eastern Saudi Arabia. (The Associated Press)

U.S. officials previously alleged at least one recent drone attack on Saudi Arabia came from Iraq, where Iran backs Shia militias. Those militias in recent weeks have been targeted themselves by mysterious airstrikes, with at least one believed to have been carried out by Israel.

Abbas Mousavi, Iranian Foreign Ministry spokesperson, on Sunday 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.

Separately, Iraqi Prime Minister Adel Abdul-Mahdi’s office issued a statement on Sunday denying the drone attack came from there.

Iraq “abides by its constitutions that prevents the use of its lands to launch aggressions against neighbouring countries,” the statement said.

The oil processing facility targeted by the attack is some 330 kilometres northeast of the Saudi capital of Riyadh. (CBC)

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 of 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.

U.S. 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 stabilization 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 seven million barrels of crude oil a day. By comparison, Saudi Arabia produced 9.65 million barrels of crude oil a day in July.

AFPTV screen grab shows smoke billowing from the facility. (AFP/Getty Images)

The Khurais oilfield is believed to produce over one million 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.