Oil prices have spiked after a devastating attack on the heart of Saudi Arabian oil production over the weekend shocked markets and could disrupt the global supply of crude for some time.

Prices initially surged as much as 18% but retreated after US President Donald Trump said on Sunday night that he had authorized the use of oil from the country’s emergency oil supply. Trump said oil from the Strategic Petroleum Reserve, or SPR, would be used “to keep the markets well-supplied.” The US reserve is the largest backup pool of oil.

State-owned Saudi Aramco oil facilities were badly damaged in the strikes and restoring production to their pre-attack levels “will take weeks, not days,” according to two Saudi sources familiar with the kingdom’s oil operations. “This is unprecedented in scale, and impact,” they said.

US oil futures were trading at more than $60 a barrel — a spike of nearly 10% — in New York on Monday morning. Futures of Brent crude, the global benchmark, traded at more than $66 per barrel, up 10%.

Gasoline futures, meanwhile, were up more than 9%.

“This is a big deal,” said Tom Kloza, chief oil analyst for the Oil Price Information Service, which monitors the price of oil across the United States. “It is the biggest shock to the oil markets since [Hurricane] Katrina. And like Katrina it will likely haunt us for months, at least weeks.”

Kloza said gasoline prices will likely “creep up” this fall, rather than drop steadily, as they historically have done.

By Laura He, John Defterios and Anneken Tappe, CNN Business