The soldiers died in Zabul province on Saturday, military spokeswoman Master Sgt. Cindy Beam said in an e-mailed statement. She gave no details of how they were killed.
"Four U.S. service members assigned to the Combined Joint Special Operations Task Force-Afghanistan were killed in action today here in southern Afghanistan," Beam said in a statement datelined Zabul.
She said the names of the soldiers would not be released pending notification of their families.
Separately, the U.S. Arny said Saturday thatas he led his team of Army Rangers up a hill during a firefight in Afghanistan last month.
Tillman walked away from a $3.6 million NFL contract to join the Army after the Sept. 11, 2001, attacks. The Arizona Cardinal safety became a symbol of patriotism to many Americans for his decision.