Crude oil prices rose again on Wednesday as the United States and Iran exchanged military strikes, ending weeks of relative calm in the Middle East and reigniting concerns over the security of oil flows through the Strait of Hormuz.

The US–Iran war is now entering its seventh month, with the latest attacks representing the largest exchange of fire between Tehran and Washington since July. US forces struck targets along Iran’s southern coast, while Tehran responded with attacks on US bases in the region.

Brent crude futures rose 98 cents, or 1%, to close at $95.63 a barrel, while US West Texas Intermediate (WTI) gained 79 cents, or 0.9%, to $91.01 a barrel.

During the session, both benchmark contracts moved sharply, with Brent and WTI alternating between gains of as much as $2 a barrel and losses of up to $1. The intraday highs for both benchmarks were their highest since July 24.

“The latest strikes represent a significant escalation after roughly a month of relative calm, with the US targeting Iranian radars and mine-laying capabilities, while Tehran responded against US positions in the region,” said Mark Shafer, director at Liquidity Energy.

“The key concern for the oil market is whether the renewed hostilities will lead to a further deterioration in actual oil flows in the region,” he added.

The war began with joint US and Israeli strikes against Iranian targets in late February. Since then, Iran has effectively restricted shipping through the Strait of Hormuz, a critical maritime route through which roughly one-fifth of global oil and LNG consumption passed before the conflict.

Countries around the world are trying to ease price pressures by seeking alternative sources of supply and drawing on their strategic reserves, which have also declined.

Iran’s Islamic Revolutionary Guard Corps (IRGC) said the US attacks would lead to further restrictions on traffic through the Strait of Hormuz.

According to preliminary data from Kpler, only four commercial vessels passed through the Strait of Hormuz on Wednesday, compared with an average of about 13 vessels over a 10-day period. The Revolutionary Guards also claimed that two oil tankers were hit by sea mines and immobilized while attempting to cross the strait.

Meanwhile, Iran added more vessels to a list of ships it considers to be violating transit rules and which could face fines, seizure, or detention.

However, US Energy Secretary Chris Wright said on Tuesday that 17 million barrels of oil passed through the Strait of Hormuz on Monday, describing it as the largest volume of crude transported since the start of the war.

At the same time, Iraq increased its oil exports in August, with shipments expected to rise further in September as high profit margins and Iran’s approval for tankers to transit the Strait of Hormuz encourage buyers.

“Although the escalation in fighting will slow transit through the Strait of Hormuz in the short term, the market has already absorbed the fact that alternative sources of crude can ultimately reach the market,” said Dennis Kissler, a senior trading executive at BOK Financial.

Meanwhile, OPEC+ is expected to keep its production policy unchanged for October, according to Reuters sources, as the group completes the unwinding of one layer of production cuts and shifts its focus toward 2027 quotas.

Elsewhere, Russia carried out another missile and drone attack on energy infrastructure in Ukraine’s Odesa region, according to Ukrainian transmission system operator Ukrenergo.

In the United States, crude oil inventories fell by 4.5 million barrels last week, according to the Energy Information Administration (EIA), compared with analysts’ forecast of a decline of just 1.1 million barrels.