Iraqi police say a bomb has exploded in central Baghdad, killing at least five people and wounding nine others.

Authorities say the blast Monday was caused by a roadside bomb aimed at a police patrol.

In eastern Baghdad, U.S. forces say an attack Saturday night on one of their convoys sparked a large fire in the Al Ummal market.

American officials said no U.S. military personnel were injured when a bomb went off next to their vehicles.

In northern Iraq, U.S. forces say they found a mass grave containing up to 30 bodies.

A news release Monday says the grave was found Sunday near the town of Muqdadiyah in restive Diyala province, north of Baghdad.

The statement says the bodies were badly decomposed and appeared to have been buried about eight months ago.

Last week, Iraqi authorities uncovered about 40 bodies from a mass grave south of Baghdad. The bodies were believed to have been buried for more than a year.

Some information for this report was provided by AP and Reuters.