Brent crude rose for a second day as the U.S. conducted airstrikes against militants in Iraq, OPEC's second-largest producer. West Texas Intermediate futures also gained.

Airstrikes have been launched against Islamic militant artillery, Pentagon Spokesman Admiral John Kirby said on Twitter. President Barack Obama yesterday authorized the strikes in parts of Iraq. Chevron Corp. and Afren Plc withdrew some staff from their operations in the country's Kurdish region.

"The airstrikes in Iraq seem to be shaking the market," said Gene McGillian, an analyst and broker at Tradition Energy in Stamford, Connecticut. "We are seeing some geopolitical risk priced into the market again."

Brent for September settlement gained 41 cents, or 0.4 percent, to $105.85 a barrel at 9:18 a.m. New York time on the London-based ICE Futures Europe exchange. The volume of all futures traded was 36 percent above the 100-day average for the time of day. Prices are up 1 percent this week.

WTI for September delivery climbed 36 cents to $97.70 a barrel on the New York Mercantile Exchange in volume that was 0.7 percent below the 100-day average. The grade is little changed this week. The U.S. benchmark crude was at a discount of $8.15 to Brent after closing at $8.10 yesterday.

Obama said the strikes, if needed, would be used to protect U.S. personnel and the Yezidis, a minority sect concentrated in northern Iraq that has been targeted by militants and are stranded on a mountain. The U.S. will strike militants if they move toward the Kurdish city of Erbil, where it has diplomatic personnel, he said.

Gold prices rose to a three-week high, as renewed geopolitical tensions in Iraq and Ukraine continues to support the demand for the precious metal as a safe haven.

Gold prices strengthened after Thursday, President Barack Obama has authorized air strikes on Iraq to crush Islamic militants in northern Iraq, and began dropping humanitarian aid to besieged areas in order to prevent "possible genocide" of religious minorities.

Meanwhile, the demand for this precious metal has also received support amid growing conflict between Russia and the West about the situation in Ukraine.

On Thursday, Moscow banned the import of products from Europe and the United States in response to the sanctions imposed because of the Ukrainian crisis.

Visiting Kiev this week, NATO Secretary General said that Moscow has focused 20000th troops at the border with Ukraine in preparation for a possible ground invasion.

Some investors believe gold is a safer asset than stocks or bonds, in times of geopolitical uncertainty.

The cost of the August gold futures on the COMEX today rose to $ 1322.10 per ounce.