Oil climbed by about 4 percent on Oct. 8 as attacks on shipping in the Persian Gulf and the Strait of Hormuz deepened supply fears, while a tropical storm threatened U.S. offshore production.

By 12:17 p.m., U.S. West Texas Intermediate crude rose by $3.47, or 3.9 percent, to $92.40. Brent crude futures had climbed by $4.20, or 4.15 percent, to $105.41 per barrel.

Oil prices had settled lower on Oct. 7 after the International Energy Agency said its members had agreed to speed up the release of emergency oil stocks and to prioritize diesel.

However, continuing threats to shipping in the Strait of Hormuz keep markets on edge.

At least nine tankers have reported being struck by unidentified projectiles since the beginning of October, according to the UK Maritime Trade Operations (UKMTO).

The incidents involved crude oil, liquefied petroleum gas, and other tankers, several of them transiting outbound. In a number of cases, the projectiles caused fires or damage to engine rooms, including one blaze on Oct. 5 that the crew was still fighting when the alert was issued.

No casualties or environmental damage have been reported so far, and in at least two cases, the crews confirmed that they were safe.

Separately, the UKMTO said a tanker heading into the strait on Oct. 5 was hailed by Iran’s Islamic Revolutionary Guard Corps (IRGC) about 11 nautical miles north of Khasab, Oman, and told to turn back or be targeted; the master complied.

The UKMTO didn’t name the party responsible for the strikes, saying only that investigations are ongoing and urging vessels to transit with caution.

The weather is also adding to the pressure on markets. Shell and Chevron said on Oct. 7 that they were cutting offshore operations in the Gulf of Mexico as Tropical Storm Isaias approached the north shore, threatening output in the United States.

This satellite image from the National Oceanic and Atmospheric Administration shows Tropical Storm Isaias off the eastern coast of Mexico on Oct. 7, 2026. (National Oceanic and Atmospheric Administration via AP)

The storm formed in the Gulf on Oct. 7 and is forecast to strengthen into a hurricane before reaching the southern U.S. coast early on Oct. 10, bringing heavy rain, storm surges, and possible tornadoes across several states, according to the National Hurricane Center.

Phil Flynn, an analyst at Price Futures Group, warned on Oct. 7 that the storm could cause shut-ins and refinery problems at a time when diesel is already tight due to the Iran war, calling a Gulf Coast hit “the last thing this market needs.”

Pressure on Shipping

The U.S. Navy-led Joint Maritime Information Center said on Oct. 4 that disruptions in the Strait of Hormuz by the IRGC demonstrate “Iran’s ⁠intent to assert presence along key transit lanes and maintain pressure ​on transiting vessels.”

Iran’s military leadership on Oct. 8 said it has reasserted its control over the Strait of Hormuz.

Iranian army commander Brig. Gen. Mohammad Hossein Dadras said Iran’s armed forces were “more prepared than at any other time.” The remarks, carried by Iran’s state-run Islamic Republic News Agency, did not address the recent attacks on shipping in the strait.

They also came after senior IRGC adviser Brig. Gen. Mohammad Reza Naqdi told the Al-Alam News Network on Oct. 7 that Tehran has “full control” of the waterway.

Vessels transit the Strait of Hormuz off the coast of the port city of Bandar Abbas in southern Iran, on Sept. 5, 2026. (Atta Kenare/AFP via Getty Images)

He added that the amount of “smuggled” oil passing through the strait was minimal and that small-boat routes used to move it to larger tankers would soon be closed.

U.S. Central Command on Oct. 7 rejected the claim, saying that Washington and its regional partners were in control of the waterway.

“Traffic is flowing through the Strait of Hormuz right now carrying commercial goods and energy supplies, including 20 million barrels of crude oil,” U.S. Central Command said.

The U.S. Energy Information Administration said on Oct. 7 that Middle East oil flows would likely stay constrained through the end of 2026, but that convoys through the Strait of Hormuz and work-arounds such as bypass routes and ship-to-ship transfers should lift regional output and exports.

Reuters contributed to this report.