Oil prices jumped above $39 a barrel on worries about the security of supplies from Iraq, Russia and Nigeria today.
Worries about oil prices, which stirred financial markets a month back, reappeared as fears about supply sent the cost of crude jumping.
Iraqi exports were halved by sabotage and Nigeria faced a possible strike.
Traders were also concerned that Russian producer Yukos may have to cut some of its exports as it struggles to finance core operations with its bank accounts frozen.
US light crude was trading at $39.23 a barrel, up 84 cents. IPE Brent was up 59 cents at $36.86 a barrel.
"The longer Iraqi exports stay affected, the closer we may creep to $40 a barrel, especially if there's any other bad news on the supply side," said Mr David Thurtell, commodities strategist at Commonwealth Bank of Australia in Sydney.
Financial markets are very wary of rising oil prices, fearing the cost could undermine the strength of the world economy and drive up inflation, prompting higher interest rates.