A bomb exploded at a Baghdad school in theShiite district of Sadr City, killing at least nine people, including at least four students. At least 41 others were wounded in the blast.

The bombing took place at about 1 p.m. local time in an area where large attacks have been infrequent because it is encircled by U.S. and Iraqi security forces and has its own neighborhood security.

The blast also wounded at least 34 people, said an Iraqi police official. A Ministry of Interior official confirmed the casualties.

Both officials spoke on condition of anonymity because they were not authorized to release the information.

There are an estimated 2.5 million Shiites living in Sadr City, a stronghold of anti-American cleric Muqtada al-Sadr.

Violence has decreased dramatically in Iraq, though insurgents continue to target civilians and security forces. The U.S. military has expressed concern of a possible rise in violence ahead of next year's national elections.

Also Monday, gunmen stormed a checkpoint north of Baghdad, killing five members of a Sunni anti-Al Qaeda group, according to a police official, who also spoke on condition of anonymity for the same reason. The U.S. military confirmed the attack.

The Associated Press contributed to this report.