Global oil prices jumped after Israel said it had struck Iran, in a dramatic escalation of tensions in the Middle East.
Benchmark oil contracts Brent Crude and Nymex light sweet were up by more than 10% after the news emerged.
Traders are concerned that a conflict between Iran and Israel could disrupt supplies coming from the energy-rich region.
The cost of crude oil affects everything from the price of food at the supermarket to how much it costs to fill up your car.
Analysts have told the BBC that energy traders will now be watching to see whether Iran retaliates in the coming days.
