NATO warplanes have launched the heaviest bombardment to date of the Libyan capital, Tripoli, in the two-month-old campaign against the regime of Col. Muammar Gaddafi. At least 15 air strikes struck the city earlier today, triggering massive explosions. The Gaddafi regime says at least three civilians were killed and 150 wounded. The bombing comes as the United States and its NATO allies are throwing more support behind Libyan rebels. On Monday, the U.S. State Department’s top Middle East envoy, Jeffrey Feltman, visited the rebel headquarters in Benghazi. Meanwhile, France and Britain have announced plans to deploy attack helicopters for operations against Gaddafi’s fighters.