The falls came despite a US government report that American crude oil stockpiles fell by more than 12 million barrels last week and are about 4% lower than average for this time of year.
Brent crude suffers biggest prICE drop in two years
Oil prICEs suffered steep falls on Wednesday after Libya said it would boost supply, even as investors fear that trade tensions will hit demand.
Brent crude dropped 6.9%-the biggest decline in more than two years-to end at $73.40 a barrel for the global benchmark.
US crude fell 5% to $710.38 a barrel-its worst one-day decline in a year.
The declines followed a months-long rally that had increased prICEs to some of the highest levels in recent years.