Oil prices hit their highest in four months after two attacks on Saudi Arabian facilities on Saturday knocked out more than 5% of global supply.
At the start of trading, Brent crude jumped 19% to $71.95 a barrel, while the other major benchmark, West Texas Intermediate, rose 15% to $63.34.
Prices eased back slightly after US President Donald Trump authorised the release of US reserves.
It could take weeks before the Saudi facilities are fully back on line.
State oil giant Saudi Aramco said the attacks cut output by 5.7 million barrels per day.
The drone attacks on plants in the heartland of Saudi Arabia’s oil industry included hitting the world’s biggest petroleum-processing facility.
US Secretary of State Mike Pompeo said Tehran was behind the attacks. Iran accused the US of “deceit.”
Later Mr Trump said in a tweet the US knew who the culprit was and was “locked and loaded” but waiting to hear from the Saudis about how they wanted to proceed.
Saudi Arabia oil supply was attacked. There is reason to believe that we know the culprit, are locked and loaded depending on verification, but are waiting to hear from the Kingdom as to who they believe was the cause of this attack, and under what terms we would proceed!
— Donald J. Trump (@realDonaldTrump) September 15, 2019
In another tweet he said there was “plenty of oil!”.