A US Marine handed out coins promoting Christianity to Muslims in the former insurgent stronghold of Fallujah, outraged Sunni officials said Friday. The US military responded quickly, removing an American trooper from duty pending an investigation. It was the second perceived insult to Islam by American service members this month. A US sniper was sent out of the country after using a Qur'an copy for target practice. Those actions threaten to alienate Sunni Arabs who have become key allies in the fight against insurgents, a movement that started in Anbar province, which includes Fallujah. Distribution of the coins in Fallujah was particularly sensitive because the city, 65 km west of Baghdad, is known for its large number of mosques. Photos of the coins, which were inscribed with phrases in Arabic, were widely distributed via cell phones in Fallujah. Sheikh Abdul-Rahman Al-Zubaie, an influential tribal leader in the city, spoke of his outrage over perceived proselytizing by American forces and warned patience was running thin. “This event did not happen by chance, but it was planned and done intentionally,” Al-Zubaie said. “The Sunni population cannot accept and endure such a thing. I might not be able to control people's reactions if such incidents keep happening.” Sunni officials and residents said a Marine distributed about 10 coins at a checkpoint controlling access to the city, scene of one of the fiercest battles of the war. Al-Zubaie accused the Marines of trying to do missionary work in Fallujah and said Sunni leaders had met with US military officials and demanded “the harshest punishment” for those responsible to make sure it doesn't happen again. Mohammed Hassan Abdullah said he witnessed the coins being handed out on Tuesday as he was waiting at the Halabsa checkpoint, although he didn't receive one himself.