(CNN) -- The leader of al Qaeda in Iraq urged his followers to kill at least one American in the next two weeks using a sniper rifle, explosive or "whatever the battle may require," according to an audiotape that aired Thursday on Al-Jazeera. The Arabic news network identified the man on the tape as Abu Hamza al-Muhajer, however CNN was unable to independently verify his identity. Al-Muhajer took command of the terror network's partner group in Iraq after an American airstrike killed its former leader, Abu Musab al-Zarqawi, in June, U.S. officials say. Al-Muhajer, which means "the immigrant," is the pseudonym adopted by Abu Ayyub al-Masri, an Egyptian militant believed to be an expert at making car bombs, U.S. officials say.
"I invite you not to drop your weapons, and don't let your souls or your enemies rest until each one of you kills at least one American within a period that does not exceed 15 days with a sniper's gunshot or incendiary devices or Molotov cocktail or a suicide car bomb -- whatever the battle may require," the speaker says on the tape. The recording is more sophisticated than past tapes released by al Qaeda in Iraq and includes sound effects such as a lion's roar, machine gun fire and a sword being unsheathed. Producers at times used echo effects on al-Muhajer's voice and included snippets of inspirational songs and verses from the Quran.