Iraqi authorities say a wave of bombings across the country has killed at least 23 people in the latest apparent effort by militants to undermine confidence in the security forces.

In Monday's deadliest attack, insurgents blew up several houses in the town of Musayyib, south of Baghdad, killing seven people.

In Baghdad's Karrada district, a car bomb exploded near a group of Shi'ite pilgrims en route to the southern holy city of Karbala for a Shi'ite religious observance. That blast killed five people.

Bombs also killed four policemen in the northern city of Kirkuk, one officer in the neighboring town of Tuz Khormato, and two people in the central town of Hillah.

A mortar attack south of Baghdad killed one Shi'ite pilgrim, while at least three other people were killed elsewhere in other attacks.

No group claimed responsibility.

But minority Sunni militants have targeted majority Shi'ite pilgrims frequently. Those militants also appear to be exploiting sectarian tensions in the ruling coalition of Shi'ite Prime Minister Nouri al-Maliki, who is under political fire.

Sunni protesters have held more than a week of anti-government protests in the western province of Anbar, demanding an end to what they see as Mr. Maliki's marginalization of their community and its representatives in his Shi'ite-led coalition.