Crude oil prices rose by more than 4% on Wednesday as renewed conflict in the Middle East heightened concerns that energy supplies through the Strait of Hormuz could be disrupted. Iran said it had stopped three oil tankers in the strait, a waterway that normally carries about one-fifth of the world’s total crude oil and gas supply. The moves followed fresh regional tensions and increased market anxiety over the security of fuel shipments.

Oil-market volatility followed Tuesday’s airstrikes by US and Saudi warplanes against Iran-backed armed groups in Iraq. The US military said the groups had carried out more than two dozen drone attacks in recent days. US Central Command said the strikes targeted groups that the Islamic Revolutionary Guard Corps had directed to attack US forces and Saudi energy infrastructure. Centcom had earlier said Iranian ballistic missiles aimed at US forces in the Middle East were intercepted.

The incidents came after a three-day pause in nearly two weeks of reciprocal nighttime attacks between the United States and Iran. Brent crude had climbed from about $72 a barrel in early July to more than $100 last week before easing during the pause. President Donald Trump said this week that an agreement was possible, but the latest events underscored the fragility of efforts toward long-term peace.