Iraqi authorities say a car bomb has killed at least 20 Shi'ite Muslim pilgrims on their way home from a religious procession in the country's south.

Police said Thursday's attack at a busy bus station in the town of Musayyib hit the pilgrims as they were returning from Iraq's shrine city of Karbala, where they performed mourning rituals for a revered figure in Shi'ite Islam. Dozens were wounded in the bombing.

No one has claimed responsibility for the attack, which has renewed fears of an increase in sectarian violence that could further destabilize the country.

The blast comes just days after a wave of bombings across the country killed 23 people. Insurgents blew up several houses in Musayyib on Monday, killing seven people. Bombings also killed people in Baghdad, Hillah and Kirkuk.

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.