At least 28 people have been killed in Iraq in a series of bomb attacks targeting Shi'ite pilgrims during an annual religious observance.

Bombings Monday at Hilla, south of Baghdad, killed at least 18 people and wounded more than 30.

In Baghdad, other bombings killed at least 10 people and wounded another 30.

Many of the victims were women and children participating in processions marking Ashura, a Shi'ite day of mourning.

Ashura commemorates the seventh-century killing of Imam Hussein, a grandson of the Prophet Muhammad, during a battle with rival Muslims.

The blasts took place at a time of heightened concern about Baghdad's ability to handle security after U.S. forces finish withdrawing at the end of the month.

The pullout will end a military presence that began with the 2003 U.S.-led invasion that toppled Iraq's late dictator Saddam Hussein.

Violence in Iraq has declined from the peak of sectarian fighting in 2006 and 2007, but insurgent attacks remain common.