Prices spiked as attacks on oil tankers escalated in the Middle East.

Oil prices have increased by four percent, with benchmark Brent crude hitting $105 a barrel after the biggest rise in attacks on shipping since the Iran war began spurred trader concerns about further supply disruptions.

Brent crude futures were up $4.05, or four percent, at $105.26 a barrel by 1215 GMT on Thursday. United States oil topped $100 a barrel for the first time since May, as West Texas Intermediate crude futures CLc1 rose $3.99, or 4.15 percent, to $100.04.

Brent prices have surged by more than 30 percent from lows touched in early August, as a permanent agreement between the US and Iran to cease attacks never materialised and fighting resumed.

Iran-aligned Houthis seized control of Yemen’s port of Mocha on Thursday, further threatening Red Sea traffic, while Gulf traffic remains restricted through the Strait of Hormuz as tanker attacks in the region have intensified in recent days.

“The recent run-up in prices lays bare the market’s approach: this conflict will last longer than anticipated even a month ago, let alone at the beginning of the summer. If oil supply and exports are diminished, the oil balance remains tight and prices remain elevated,” PVM analyst John Evans said.

Iran said it had attacked 10 ships near the Strait of Hormuz on Wednesday, after the US hit five Iranian oil tankers. Iran’s Islamic Revolutionary Guard Corps said it would escalate its response to any further attacks.

While fears of prolonged and more severe supply disruptions in the Gulf have lifted Brent above $100, analysts say the durability of the rally will hinge on China.

Chinese demand

China, the world’s largest crude importer, has stepped up purchases in recent weeks after months of subdued demand, boosting physical crude markets, ING analysts said in a note.

If Chinese buying continues to recover, it could amplify the impact of any supply disruptions and drive prices higher, while a pullback in imports could temper market gains, ING said.

“For months, the bearish case rested on soft Chinese demand,” said David Jorbenaze, global oil market lead at commodities information provider, ICIS.

Rising oil prices have worsened worries about inflation and cranked up pressure within the bond market, helping to lower stocks again on Wall Street.

The S&P 500 fell 0.6 percent and is on track for a fourth straight loss.

The increase in oil prices has pushed the price for a gallon of regular petrol to an average of nearly $4.28 across the US, according to the American Automobile Association. That is not only costing more at the pump but also through higher prices for all kinds of products that move by truck to store shelves.

Following Thursday’s reports, traders are betting on a close to 70 percent chance the Fed will raise the federal funds rate at its meeting next week. That’s up from the 61 percent probability seen the day before, according to data from CME Group. That’s also despite President Donald Trump’s consistent lobbying for interest rates to go lower rather than higher.