Brent advanced 0.8 percent. Ukraine sent armored vehicles and artillery to retake Slovyansk, a stronghold for pro-separatist forces, defying President Vladimir Putin’s demand to pull back troops with Russia’s army massed across the border. WTI reduced weekly losses as the unemployment rate dropped to 6.3 percent in April, the least since September 2008.

“Ukraine is engaging in a big military way and Brent is having greater value due to geopolitical influences of Ukraine,” Tom Finlon, Jupiter, Florida-based director of Energy Analytics Group LLC, said by phone. “The unemployment number is construed positively for increases in petroleum demand.”

Brent for June settlement climbed 83 cents to close at $108.59 a barrel on the London-based ICE Futures Europe exchange. The volume of all futures was 4.9 percent above the 100-day average. Prices decreased 0.9 percent since April 25, the first weekly drop since April 4.

WTI for June delivery advanced 34 cents, or 0.3 percent, to end at $99.76 a barrel on the New York Mercantile Exchange. The volume of all futures traded was 12 percent below the 100-day average. Prices dropped 0.8 percent this week. The European benchmark was at a premium of $8.83 a barrel to WTI, compared with $8.34 yesterday.