The BBC earlier Sunday reported a statement that the group had killed Cpl. Wassef Ali Hassoun appeared on two Islamic Web sites. But Sunday, on its own Web site, Ansar al-Sunna denied responsibility for the statement.
Ansar al-Sunna had threatened to kill Hassoun unless all Iraqi prisoners held by coalition forces in Iraq were released. That statement was made last Sunday on videotape broadcast on al-Jazeera TV.
Lebanon's Foreign Ministry said Sunday it believed Hassoun, of Lebanese descent, had been beheaded. The U.S. military has not confirmed the beheading.
Hassoun immigrated to the United States from Lebanon four years ago and obtained U.S. citizenship, his father in Tripoli said.
His father called on those holding his son hostage for the last two weeks to release him because he is a Muslim and an Arab.