Fourteen Americans have been killed in Afghanistan in two separate helicopter accidents. Seven US troops and three civilians lost their lives in a helicopter crash in southern Afghanistan, while in another incident two coalition choppers collided killing four US servicemen. Hostile fire has been ruled out in both cases.Meanwhile, in the capital Kabul Afghans have clashed with police over what demonstrators claim was the desecration of the Koran by foreign troops. Protesters claim soldiers burned a copy of the holy book during a raid in the east of the country last week. The NATO-led force deny any such incident and blame the Taliban for spreading malicious rumours. Police arrested up to 30 during the demonstration as tensions are high ahead of the November 7th presidential run-off.