NEW YORK (AP) — The average price for a gallon of gasoline jumped 11 cents overnight in the U.S., and drivers in Europe waited in line to fill their tanks with fuel, as war engulfed the Middle East and shipments of oil and gas were stranded in the Persian Gulf.

Depending on the duration of the war, the pain of higher prices could increase in the coming weeks, and may be felt more heavily in areas reliant on imports.

“Right now, the worst of it is centered on Europe, because Europe is a net importer,” said Susan Bell, senior vice president of commodity markets at Rystad Energy. Diesel prices spiked 27% in Europe since Friday, rising about 62 cents per gallon, she said. “It’s gone up substantially, because Europe is so constrained on diesel supply.”

In the U.S., a gallon of regular was selling for $3.11 on average, according to motor club AAA, surprising some drivers at the pump. Gasoline prices were already rising before the U.S. launched strikes on Iran as refiners switch over to summer blends of fuel. Summer blends of gasoline are more expensive because additives are included to help keep the gasoline from evaporating in the heat, and prices tend to increase as demand for fuel rises in the summer months, said Aixa Diaz, AAA spokeswoman. Adding to the pressures, crude prices rose sharply in recent days because of the war.

Anne Dulske paid $15 more than usual to fill up her tank at a Jackson, Mississippi gas station on Tuesday.

“It’s going to affect everything in our lives,” she said. “It’s very scary, and it does hit closer to home than people think.”

Dulske, who said she had previously noticed gas prices slowly going down, called the increase surprising and said she was caught off guard when she learned the United States and Israel had attacked Iran over the weekend.

“We are knee-deep into the gas price increases,” said Patrick DeHaan, head of petroleum analysis at GasBuddy, a technology company that helps people find cheap gasoline. DeHaan estimates gasoline price could rise further, but he doubts the price would reach $4 a gallon in the U.S. “Many Americans seem very panicked that prices could hit multiple dollars higher than that, which at this point, I wouldn’t say anything’s impossible, but certainly it’s quite improbable based on the current developments.”

While the U.S. is a net exporter of oil, which is a key component in gasoline, that doesn’t make the country or its consumers immune to higher prices. Oil is traded on a global market, so price increases are felt even within the U.S. Plus, the oil produced in the U.S. is mostly light, sweet crude, and refineries on its coasts are typically geared to process heavier, sour crude, so imports are needed.