Oil traded near the highest price since December on concern that Middle East supplies may be disrupted as Saudi Arabia expanded its military campaign against Yemen.

Futures were little changed in London after capping a third weekly gain. Saudi Arabia deployed National Guard troops to its southern borders, state-run Saudi Press Agency reported, a month after launching airstrikes against Houthi rebels in Yemen. In Libya, members of the Petroleum Facilities Guard shut the Elephant oil field Saturday over unpaid salaries, said Mohamed Elharari, a spokesman at National Oil Corp.

Oil has advanced more than 18 percent this month amid speculation that unrest in Yemen may spread in the world's biggest crude-producing region. The country's location at the Bab el-Mandab, a chokepoint in international shipping, makes it important for energy trade, according to the U.S. government.

"Brent is getting support from the increased risk premium related to what's happening in Yemen," Ric Spooner, a chief strategist at CMC Markets in Sydney, said by phone. "While not imminent, there is a possibility to a disruption to shipping."

Brent for June settlement was at $65.29 a barrel on the London-based ICE Futures Europe exchange, up 1 cent, at 11:20 a.m. Sydney time. The contract climbed 43 cents to $65.28 on Friday, the highest close since Dec. 9. The European crude traded at a premium of $8.16 to West Texas Intermediate, the U.S. marker.

WTI for June delivery was 3 cents lower at $57.12 a barrel in electronic trading on the New York Mercantile Exchange. Prices have risen the past six weeks. The volume of all futures traded was about 72 percent below the 100-day average.