Oil prices extended gains on Thursday, with Brent holding above $100 a barrel as escalating Iran-US attacks on shipping heightened concerns over further disruptions to Middle East crude supplies.Brent crude futures rose 0.1% to $101.34 a barrel by 0107 GMT, while US West Texas Intermediate crude gained 0.5% to $96.55.Brent settled $3.29, or 3.4%, higher at $101.21 a barrel on Wednesday after touching $101.58. WTI rose $3.02, or 3.25%, to $96.05. Both benchmarks closed at their highest levels since May 22.The gains came after Iran said it had attacked 10 ships near the Strait of Hormuz, while the United States sank five Iranian oil tankers. Iran’s Revolutionary Guard Corps also warned that it would step up its response to further attacks.Strait of Hormuz in focusThe Strait of Hormuz remains a key flashpoint for global energy markets. Nearly one-fifth of the world’s oil supply passed through the strategic waterway before the war, but oil and gas flows through the strait have remained well below pre-war levels.Oil prices had mostly stayed below $100 a barrel since late May as traders expected the conflict to remain contained. Prices had also eased after the US and Iran reached a temporary agreement to halt attacks in June, although no permanent peace deal was reached.Brent has surged as high as $126.41 a barrel since the war began on February 28, reaching that peak on April 30. It briefly crossed $100 again in late July before falling back below the level.The International Energy Agency has forecast global oil supply to fall by 4.3 million barrels per day this year, or about 4%, adding to concerns over tighter supplies.Fuel prices add to pressureThe physical crude market is already reflecting the impact of supply disruptions. Dated Brent, a benchmark used to price around two-thirds of global oil supplies, has remained above $100 a barrel since September 3, according to LSEG data.Refined fuel prices have also remained elevated. US gasoline prices are averaging about $4.22 a gallon, while diesel prices are at record levels and approaching $6 a gallon.Higher crude prices could further raise the cost of gasoline, diesel and jet fuel, increasing transportation costs and pushing up prices of goods that rely on road, air or sea transport.Asian stocks fell on Thursday as oil prices stayed above $100, adding to investor concerns ahead of US inflation data that could influence the Federal Reserve’s monetary policy.