Death toll in Baghdad for June nearly twice that of May . U.S. official tells CNN that potential threat from ISIS with troop surge . US send in more troops to Baghdad as protection force . Mortar rounds strike gate of holy site in Samarra .
Death toll in Iraq for June nearly twice that of May . U.S. official tells CNN that potential threat from ISIS prompted troop escalation . Pentagon sending 300 more troops to Baghdad as protection forces . Mortar rounds strike gate of holy site in Samarra .