U.S. crude fell below $60 a barrel on Thursday, the first time in five years that it breached the psychologically-important support level, as oil markets extended this week's losses on oversupply concerns.

New York Mercantile Exchange's front-month West Texas Intermediate contract for U.S. crude settled down 99 cents, or 1.6 percent lower, at $59.95 per barrel, its lowest close since July 14, 2009. WTI crude continued to slide in after-hours trading and was last down nearly 3 percent to $59.20 in electronic trading.