WASHINGTON (Reuters) - Intelligence on the rebels battling Libya's Muammar Gaddafi has shown "flickers" of al Qaeda or Hezbollah presence, NATO's operations commander said, but U.S. officials said there were no indications militant groups are playing a significant role in Libya. "We are examining very closely the content, composition, the personalities, who are the leaders of these opposition forces," Admiral James Stavridis, NATO's supreme allied commander for Europe and commander of U.S. European Command, said in testimony to a U.S. Senate hearing on Tuesday. But several national security officials quickly and firmly denied that al Qaeda or Hezbollah were significantly...