WASHINGTON, Aug 18 (Reuters) - The U.S. Federal Aviation Administration (FAA) said late Wednesday that domestic air carriers and civilian pilots can fly into Kabul to conduct evacuation or relief flights with prior U.S. Defense Department approval. In a statement, the FAA said that without prior approval, U.S. carriers cannot fly over Afghanistan airspace or fly into Hamid Karzai International Airport in Kabul. The FAA cited "a lack of high altitude air traffic control services." All relief flights into Kabul "must have permission" from the Defense Department, the FAA said. Without prior approval, U.S. passenger and air carriers are prohibited from flying over nearly all of Afghanistan, the FAA said, adding it does not apply to Defense Department operated flights. There is no indication yet the Defense Department will seek to use U.S. carriers as part of the massive planned evacuation effort of thousands of people. A White House official told reporters late Wednesday the U.S. mlilitary in the last day evacuated approximately 1,800 individuals on 10 C-17s. Since August 14, the United States have evacuated nearly 6,000 people. The FAA issued a new "Notice to Airmen" late Wednesday that imposed the new restrictions barring flights over Afghanistan without prior approval, citing risks "posed by extremist/militant activity, limited risk mitigation capabilities and disruptions to air traffic services." A Pentagon spokesman told reporters Monday that the U.S. military had assumed control of air traffic control at the Kabul airport. United Airlines said late Sunday it was rerouting some U.S. to India flights to avoid Afghanistan airspace after insurgents took control of the presidential palace in Kabul. The order does allow for some limited jet routes for some transiting flights over Afghanistan and also urges carriers to minimize time spent below 26,000 fleet. In late July, the FAA issued new restrictions on Afghanistan U.S. air operations, saying flights operating below 26,000 feet were prohibited over nearly all of Afghanistan, unless operating in and out of Kabul, citing the risk "posed by extremist/militant activity." Reporting by David Shepardson; Editing by Himani Sarkar and Michael Perry Our Standards: The Thomson Reuters Trust Principles.