Oil fell in price by 8.8% to below $US46 per barrel on Monday.
US crude for May delivery settled 8.8% lower at $45.88 per barrel, down $US4.45. Brent crude for June settled 6.5% lower at $US49.86, down $US3.49.
Oil is almost $US100 below a record high of $US147.27 reached on 11 July last year.