Bloomberg: New York officials have increased security with frozen zones, truck inspections and heavily armed police after reports of a credible, uncorroborated threat that al-Qaeda may be plotting an assault in the city today, the tenth anniversary of the 2001 terrorist attacks. A decade ago, a group of men tied to the terrorist group hijacked four airliners, flying two into the World Trade Center towers in New York; a third into the Pentagon in Arlington, Virginia; and crashing a fourth in Shanksville, Pennsylvania, after passengers thwarted the hijackers. Close to 3,000 people were killed that day.