BAGHDAD  An American marine guarding a checkpoint on the western outskirts of Falluja handed out coins with an Arabic translation of a biblical verse to Iraqis entering the city, angering residents and city leaders who denounced it as a serious affront to Islam and an attempt to convert them to Christianity.

As the Marines quickly apologized on Thursday for the episode, Sunni guerrillas struck several times in northern Iraq, killing at least 19 people in two suicide bombings. Gunmen near Tikrit also used a water tanker to attack an Iraqi checkpoint, but the Iraqi security forces repelled the assault and killed 14 attackers.

In Falluja, a city just west of Baghdad, the Marines pledged to discipline the marine who handed out the coins, which were inscribed with one of the Bible’s most widely known verses, John 3:16: “For God so loved the world, that he gave his only begotten son, that whoever believes in him shall not perish, but have eternal life.”

American military officials in Baghdad emphasized Thursday that military regulations barred service members in Iraq from “proselytizing any religion, faith or practices.”