The benchmark US oil contract increases more than 2.5 per cent when markets open, as Mideast tensions rise with new US attacks on Iran, AFP reports.
West Texas Intermediate crude, one of the two major global benchmarks, was up 2.63pc at $72.29 per barrel.
Oil prices are still well below the peaks they shot up to as the war began in late February and Iran largely shut down the Strait of Hormuz.
