The U.S. military denied a report carried by an independent Afghan news agency Tuesday that said three rockets were fired at a U.S. special forces base in eastern Afghanistan. The Pakistan-based Afghan Islamic Press (AIP) quoted residents as saying that U.S. aircraft were scrambled after the overnight attack on the air field in the city of Khost but took no retaliatory action. Tina Kroske, a spokeswoman for the U.S. military at Bagram Air Base just north of Kabul, dismissed the report. "It didn't happen," she said. "I don't know where these reports are coming from." AIP described the attack as the latest in a string of mostly ineffective strikes targeting U.S. forces in the area. Khost was a stronghold of Afghanistan's ousted Taliban regime and of the al Qaeda network of Osama bin Laden blamed for the September 11 attacks on the United States. It borders Pakistan's semi-autonomous tribal areas, where remnants of the Taliban and al Qaeda are believed to have sought refuge. U.S. military officials in Afghanistan said earlier on Tuesday that six U.S. airmen were slightly hurt when a helicopter that had carried a wounded civilian from Khost made a hard landing at Orgun-e, in the eastern province of Paktika. Colonel Roger King, a spokesman at Bagram, said the HH-60 helicopter flew about 100 feet at the U.S. special forces base at Orgun-e before making an "inadvertent landing." "It was like the takeoff was aborted, and it came down, hit hard," King said. Six airmen on board were treated for minor injuries at the scene and released, he said, adding that the cause of the accident was being investigated. King said the wounded civilian, a truck driver, was hurt in an ambush between the cities of Gardez and Khost Tuesday morning and may have been carrying supplies for American-led military operations. The United States launched air strikes on Afghanistan last year which ousted the Taliban from power. U.S.-led coalition forces some 12,000 strong are still hunting for remaining al Qaeda and Taliban fighters. Al Qaeda has vowed to avenge the military campaign, which is believed to have killed several hundred Afghan civilians. Around 40 American soldiers have been killed in combat and non-combat incidents and more than 340 have been wounded since U.S. operations in Afghanistan began last October.