Brent touched $110 a barrel for the first time since May on Friday on worries that escalating tensions in the Middle East could further tighten supplies, while investors assessed how much diesel Russia could supply to the global market.

Brent crude futures settled $3.94, or 3.7%, higher at $109.86, the highest since May 19, while US West Texas Intermediate crude futures closed $3.44, or 3.5%, higher at $101.41, the highest since September 17.

So far this week, Brent has risen 4.9% and WTI 10.4%.

“WTI and Brent reversed earlier losses as escalation fears resurfaced amid rumours of attacks on Saudi energy infrastructure,” research and consultancy Energy Aspects said in a note.

“Israeli reports suggest Iran may be preparing a pre-emptive strike following unusual military movements detected by Western intelligence. Although unverified, these developments reinforce our view that persistent escalation risks will keep flat prices supported,” Energy Aspects added.

A Saudi-led coalition said it intercepted and destroyed a ballistic missile launched towards the Red Sea city of Yanbu. The port is critical for Saudi Arabia’s efforts to bypass the Strait of Hormuz and keep oil flowing to international markets.

Initial reports indicated no damage to Yanbu’s infrastructure, consultants Rapidan Energy Group said.

Supply concerns also increased as attacks around the Strait of Hormuz surged over the past 10 days, with Iran saying it was stepping up strikes in response to the US blockade of its ports and tougher sanctions introduced last month.

“Intensified Iranian attacks drove Gulf crude flows sharply lower,” Kpler analysts said in a report on Thursday, adding that they expected a slower and more uneven recovery in Hormuz flows in the absence of a comprehensive political deal.

Russia Refinery Attacks

Ukraine struck a Russian oil refinery on Thursday after President Volodymyr Zelenskiy declared that Kyiv was abandoning a ceasefire covering energy sites announced by US President Donald Trump and criticized Trump’s willingness to strike deals with Moscow.

Russia’s Ryazan oil refinery has suspended operations at a primary crude distillation unit following a drone attack in the region on Thursday, two industry sources told Reuters.

“Conflict in the Middle East still keeps coming back and I think it’s questionable how much diesel fuel Russia can actually deliver to the markets. Those two factors are just continuing to have traders be buyers,” said Dennis Kissler, senior vice president of trading at BOK Financial.

To boost supply, the International Energy Agency agreed on Thursday to release more than 20 million barrels of fuel to the market.

The United States also issued a request for proposal for an exchange of up to 17 million barrels of crude oil from the nation’s Strategic Petroleum Reserve, the Department of Energy said on Friday.

Washington previously agreed to loan 172 million barrels of oil from the SPR as part of a wider deal with about 30 countries in the International Energy Agency to release 400 million barrels from reserves around the world.

Brent crude was little changed on Thursday, while WTI settled up more than 3% after news that the US was weighing plans to ease restrictions on the world’s “shadow fleet” of tankers and after a big US crude stock draw on hurricane production shut-ins.

(Reporting by Enes Tunagur in London, Sam Li in Beijing and Siyi Liu in Singapore; additional reporting by Stephanie Kelly in London. Editing by Mark Potter, Alexander Smith, Louise Heavens and Sanjeev Miglani)