** S&P 500 energy index .SPNY gains 3% as oil prices edge higher on geopolitical concerns

** Brent crude LCOc1 futures up 3.8% at $71.01/barrel; U.S. West Texas Intermediate $(WTI)$ crude futures CLc1 rise 4% to $65.75/barrel

** Brent futures surged to a near six-month high on rising concerns about a possible U.S. military attack on Iran, OPEC's fourth-largest producer with output of 3.2 million barrels per day O/R

** Oil majors Exxon Mobil XOM.N and Chevron CVX.N gain 3.2% and ~3%, respectively

** APA Corp APA.O, Occidental Petroleum OXY.N, ConocoPhillips COP.N and Halliburton HAL.N among biggest percentage gainers on the energy index, up between 3.1% and 5.1%

** Meanwhile, refiners Phillips 66 PSX.N gains 3.6% and Marathon Petroleum MPC.N rises ~5%

** Oilfield services companies SLB SLB.N rises 3% and Baker Hughes BKR.O up ~8%

(Reporting by Dharna Bafna in Bengaluru)

((Dharna.bafna@thomsonreuters.com))