BAGHDAD — An American soldier used a Quran, the Islamic holy book, for target practice in a predominantly Sunni area west of Baghdad, prompting an apology from the U.S. military, a spokesman said Sunday.

Separately, mortar shells slammed into a residential area north of the Iraqi capital, killing at least four people and wounding 30, most children playing outside, officials said Sunday.

The shelling occurred as clashes broke out in Shiite areas late Saturday despite a truce reached last week by Shiite politicians and followers of anti-U.S. cleric Muqtada al-Sadr.

Iraqi police found the bullet-riddled Quran with graffiti inside the cover on a small-arms range near a police station in Radwaniyah, a former insurgent stronghold west of Baghdad, U.S. military spokesman Col. Bill Buckner said in an e-mailed response to a query.

American commanders then launched an inquiry that led to disciplinary action against the soldier, who has been removed from Iraq, Buckner said.

The shooting, which occurred May 9 and was discovered two days later, threatened to further strain relations between the Americans and Sunni allies who have joined forces with them against al-Qaida in Iraq in Radwaniyah and other areas.

The Association of Muslim Scholars, a Sunni group, condemned the shooting of the Quran, calling it "a hideous act against the book of almighty God and the constitution of the nation and the source of its glory and dignity."

The incident was first reported by CNN, which broadcast a ceremony at which the top American commander in Baghdad apologized to tribal leaders in Radwaniyah. The military confirmed the details in an e-mailed response to a query.

"I come before you here seeking your forgiveness," Maj. Gen. Jeffery Hammond was quoted as saying. "In the most humble manner I look in your eyes today and I say please forgive me and my soldiers."

The commander also read a letter of apology by the shooter, and another military official kissed a Quran and presented it to the tribal leaders, according to CNN.

The military statement called the incident "serious and deeply troubling" but stressed it was the result of one soldier's actions and "not representative of the professionalism of our soldiers or the respect they have for all faiths."

The Sunni alliances have been key to a steep decline in violence over the past year, along with a U.S. troop buildup and a longer term cease-fire by al-Sadr's Mahdi Army militia.