LONDON -- Global oil prices spiked 20% when markets reopened on Monday, after a weekend attack on Saudi Arabia's oil facilities suspended the production of 5.7 million barrels a day. That amounts to roughly 5% of the world's total daily crude oil production.
State-run oil company Aramco said in a statement that work was underway to restore production.
The U.S. has blamed Iran for launching nearly a dozen cruise missiles and over 20 drones from its territory into a key Saudi oil facility on Saturday. Saudi authorities said the weapons were Iranian, but stopped short of blaming Iran directly for the attack.
The Houthi rebels in neighboring Yemen claimed responsibility for the assault, which hit one of the world's largest oil processing facilities, hundreds of miles from the Yemen-Saudi border, and sharply impacted global oil supplies.
But a senior U.S. official told ABC News that was false: "It was Iran. The Houthis are claiming credit for something they did not do."
Secretary of State Mike Pompeo first blamed Iran on Saturday, tweeting that there was "no evidence the attacks came from Yemen."
Iran has denied responsibility for the attack, accusing Pompeo of "max deceit," as the country's Foreign Minister Mohammad Javad Zarif tweeted Saturday.
Brent Crude, which is used primarily as a reference price benchmark for buying and selling oil in Europe and the Middle East, gained around 20% as trading opened Monday, before stabling around 10% as the day continued. The U.S. benchmark, West Texas intermediate crude, jumped around 10%, according to the AP.
In terms of gross peak supply loss in millions of barrels of crude today, the suspension of 5.7 million is the largest on record, according to the International Energy Agency. The last disruption of a comparable size came in 1978-9 during the Iranian Revolution, when the production of 5.6 million barrels of crude were suspended today.
Dr Valérie Marcel, an associate fellow of Energy, Environment and Resources at think tank Chatham House, told ABC News said the main immediate significance of the attack was "cutting Saudi Arabian production in half."
"The immediate issue is getting supplies to the customers that are expecting their crude deliveries, and so Aramco is taking measures to be able to meet demand," she said. "The economic expectations for the country, really it depends completely on the timeline. How long will this disruption last?"
The stabilization of oil prices a few hours after the market opened means that currently there is "not a huge concern" of the price having an impact on important global economies, she said, but if the disruption were to last several weeks, that could change.
Meanwhile, the international community has moved to condemn the attacks on the Saudi oil facilities.
"Just spoke to @SecPompeo about this egregious attack on the security of Saudi Arabia," the U.K. Foreign Secretary Dominic Raab tweeted on Sunday. "This was a reckless attempt to damage regional security and disrupt global oil supplies. The UK condemns such behaviour unreservedly."
Russia has also condemned the attacks, but warned the U.S. against retaliatory strikes on Iran, after President Trump said the U.S. was "locked and loaded."
"We decisively condemn the strikes on non-military targets" and "the negative consequences arising from this for the world economy," the Foreign Ministry said in a statement. "We firmly recommend against not rushing to any conclusions about who committed this attack on the Saudi oil refineries. We consider it counterproductive to use this event for the inflaming of passions around Iran along the well-known lines of the U.S. And even more unacceptable are the options that are being presented, the envisaged retaliatory strikes which are allegedly being discussed at the present time in Washington."