Oil prices continued a months-long slide on Monday, briefly hitting five-and-a-half-year lows. U.S. crude futures fell by more than 2.5 percent to as low as $56.25 a barrel before inching up again. Prices have fallen by more than 40 percent this year, and energy industry analysts expect further declines. "The template is still in place," market analyst Alastair McCaig told Reuters. "Over-supply and dwindling demand mean that the pressure will still be on oil."