At least 14 Americans were killed in two helicopter collided on Monday, military officials said. It was one of the deadliest days of the war for U.S. troops.

Quoting military sources, NBC News reported that seven American servicemen and three U.S. civilians were among the dead in a crash in the country’s west. Meanwhile, a US Army Ch-47 Chinook helicopter seen in operation in southern Afghanistan. Two helicopters collided in southern Afghanistan, killing four American troops and wounding two more, the military said.

Eleven American servicemen, one U.S. civilian and 14 Afghan civilians were also injured in the crash in western Afghanistan.

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