Multiple explosions occurred "in the vicinity of Jalalabad Airfield" in eastern Afghanistan, an allied military spokesman said Sunday.
Jamie Graybeal of the International Security Assistance Force said he has not seen any reports of Taliban getting on to the base, though he added officials were still "on the scene gathering facts."
Jalalabad is in eastern Afghanistan, about midway between the Afghan capital of Kabul and the western Pakistani city of Peshawar.
The city is the capital of Nangarhar province, which borders Pakistan's volatile Khyber Pakhtunkhwa province. Terrorists and militants have been active in Nangarhar, which includes Tora Bora -- where the late al Qaeda leader Osama bin Laden escaped after a 2001 battle with coalition forces.
And the Jalalabad airfield, which contains U.S. troops, has been targeted before. Last April, four suicide bombers wearing women's burqas tried to launch an attack there, airfield commander Jahangir Azimi said at the time.