A massive truck bomb ripped through the United Nations headquarters in Baghdad, killing at least three people and wounding scores, witnesses said. It may have been a suicide attack, a top U.S. official said. Among those badly hurt was Secretary-General Kofi Annan’s special representative to Iraq, Sergio Vieira de Mello. A U.N. official said the diplomat was trapped in his wrecked office, which appeared to be the target of the unidentified bombers. Clouds of black smoke floated skyward, ruffling the world organization’s sky blue flag in the late afternoon air. U.N. workers said many colleagues were still missing in the rubble. There was no claim of responsibility, just as there was none two weeks ago when a truck bomb shattered the Jordanian embassy in Baghdad, killing 17 people. The U.S. occupation forces say Muslim militants or diehard supporters of Saddam Hussein might have set that bomb to destabilize American rule in Iraq. Full Story