Oil prices tumbled after a meeting by major exporters in Qatar collapsed without an agreement to freeze output , leaving the credibility of the OPEC producer cartel in tatters and the world awash with unwanted fuel.
Tensions between Saudi Arabia and Iran were blamed for the failure which revived industry fears that major government-controlled producers will increase their battle for market share by offering ever-steeper discounts.
Oil prices have fallen by as much as 70 percent since mid-2014 as producers have pumped 1 to 2 million barrels of crude every day in excess of demand.