July 26 (Reuters) - The U.S. Federal Aviation Administration (FAA) said on Monday it has imposed new flight restrictions over Afghanistan for U.S. airlines and other U.S. operators in response to the changing security environment. The FAA, in an emergency order effective Sunday, said flights operating below 26,000 feet are prohibited in the Kabul Flight Information Region, which largely covers Afghanistan, unless operating in and out of Hamid Karzai International Airport, citing the risk "posed by extremist/militant activity." The restrictions do not apply to U.S. military operations.