Crude oil prices rise around 1 percent after Saudi launches operation in Yemen
The operation, against Houthi rebels who have driven the president from the country's capital, could stoke concerns about the security of oil shipments from the Middle East.
Analysts had earlier said they were worried a proxy war might break out on the Arabian peninsula, home to the world's biggest oil fields, if the conflict drew in Saudi Arabia and rival Iran.
Brent futures for May delivery had climbed just over 1 percent, or 62 cents, to $57.10 a barrel by 2106 ET, after rising as high as $57.25 in earlier trade.
U.S. crude for May delivery was up 50 cents at $49.72 a barrel, after trading as high as $49.90.
Saudi Arabia announced on Wednesday it had launched military operations in Yemen, carrying out air strikes in coordination with a 10-country coalition seeking to beat back Houthi militia forces besieging the southern city of Aden where President Abd-Rabbu Mansour Hadi had taken refuge.
(Reporting by Aaron Sheldrick)