International oil prices moved closer to $100 a barrel on September 8 as military tensions involving major Middle East oil producers intensified. Brent crude futures on ICE Futures Europe in London rose more than 2% from the previous session to $99.25 a barrel, while West Texas Intermediate futures climbed 2.6% to $93.91. Iran-backed Houthi rebels in Yemen said they attacked Saudi Aramco refining facilities and air bases in Saudi Arabia, describing the strikes as retaliation for recent Saudi-led coalition air raids on key areas of Yemen. Separately, clashes between the United States and Iran continued after the Islamic Revolutionary Guard Corps fired a ballistic missile at a U.S. Navy warship on September 6. U.S. forces then struck three Iranian oil transport vessels, while the IRGC later said it had attacked tankers and other vessels linked to the United States. The continuing conflict has heightened concern that crude supply from the region could be disrupted.