Crude oil prices surged on Wednesday after Saudi Arabia carried out airstrikes on Iran-backed militants in Yemen.
Brent crude prices increased 5% to $59 a barrel and US WTI Crude rose 6% to $52 a barrel, amid concerns over oil shipments in the region.
Some traders feared the air strikes were a sign that fighting in the region had escalated out of control, although there was little threat to immediate supplies in the oil-rich Middle East.
Riyadh launched airstrikes against Houthi rebels, who had earlier forced the country's President to flee by boat to Oman. The Houthis have received backing from Iran, which like Saudi Arabia, is a major oil exporter.
The rival producers have long been engaged in a race for regional dominance, with each country aggressively exporting its own security, economic and religious interests.
Yemen also has a vital role as shipping lanes from the region to Europe pass close to its eastern coastline. The waters between Yemen and Djibouti, the Bab el-Mandab strait, are 40km (25 miles) wide and are heavily militarised.