The war in Iran has caused a spike in gas prices that is hitting California consumers especially hard, according to data from the American Automobile Association (AAA).

AAA reports that in California, the most expensive US market for gas, the average price per gallon on Monday was $5.20, compared to $3.47 nationally. The national average climbed nearly $0.50 since the conflict began more than a week ago, while in the Golden state it rose by $0.55.

Since the US and Israel launched attacks on Iran on 28 February, leading to intensifying violence across the Middle East, the price of oil surged to more than $100 a barrel for the first time in nearly four years. The conflict has damaged oil and gas facilities and stranded ships carrying roughly 20m barrels of oil a day in the Gulf.

About 20% of the world’s oil is shipped through the Strait of Hormuz every day but the channel has essentially been closed for the last week.

Currently 9m barrels of oil a day are off the market due to attacks on facilities or producers taking precautionary measures, said Claudio Galimberti, the chief economist at Rystad Energy.

“Right now, with all of this shut in, we are in a situation of extreme deficit,” he said.

Prices were already expected to rise with growing demand this time of year and the production of summer-blend gasoline. But the conflict has led to steeper increases in fuel prices. A Chevron in Los Angeles was charging $8.21 a gallon, ABC7 reported.

“I drive Uber and I’m just getting killed right now, and I mean gas prices are just so high … they were high before the war,” one driver told the outlet.

Donald Trump has dismissed concerns about the surge, arguing prices will “drop very rapidly” when the conflict ends, while his administration has insisted the increases would last weeks rather than months.

Karoline Leavitt, the White House press secretary, described the rise in prices as “a short-term disruption for a long-term gain of taking out the rogue Iranian terrorist regime and finally ending their restriction on the free-flow of energy through the straits of Hormuz”.

Californians pay more for gas than any other state in the US, primarily because of taxes, environmental regulations and a sharp drop in refining capacity. But Gavin Newsom’s office has said the blame for this increase lies solely with the president.

“Average gas prices in California have stayed below $5 for nearly two years – until now,” the governor’s office said in a statement on social media. “This is because of Trump’s war with Iran.”

The Associated Press contributed reporting