Letter from al Qaeda in U.S. militant found after he was slain , Iraq says . Letter urges al Qaeda in Iraq to fight against Sunni -backed American militias . It also cautions vigilance against allowing the `` enemy '' to infiltrate its apparatus and exhorts its fighters to keep silent about operations . Document also cautions vigilance against infiltrators .
Letter from al Qaeda in U.S. militant found after he was slain , Iraq says . Letter urges al Qaeda in Iraq to fight against Sunni -backed American militias . Document also cautions vigilance against infiltrators .