KABUL - Four rockets hit Afghanistan's Bagram airfield late on Monday evening, destroying a helicopter belonging to the NATO-led forces, killing three Afghan personnel inside, a spokesman for the coalition said on Tuesday.Two more personnel belonging to NATO's International Security Assistance Force (ISAF), who were also in the helicopter, were injured, he said.The helicopter was on a ramp in the airfield when the rockets hit. The attack comes on the 11th anniversary of the September 11 attacks.