NEW : Battle lasted 12 hours as hundreds of militants fired on outpost , official said . Eight American soldiers , two members of Afghan National Security Force killed in fighting . The Wanat attack was the deadliest attack on U.S. troops in three years , and prompted a Pentagon investigation . Coalition forces said they called in airstrikes , repelled attack from militants . Incident marks deadliest day for U.S. troops in Afghanistan since 2008 .
NEW : Battle lasted 12 hours as hundreds of militants fired on outpost , official said . Eight American soldiers , two members of Afghan National Security Force killed in fighting . Coalition forces said they called in airstrikes , repelled attack from militants . Incident marks deadliest day for U.S. troops in Afghanistan since 2008 .