A car bomb has exploded outside a Shi'ite mosque in the Iraqi town of Hillah, killing at least 25 people as Iraqi Shi'ites observed the first day of the holy month of Ramadan.

Police say nearly 90 others were wounded Wednesday evening as the faithful gathered at the mosque to pray before breaking their fast.

The attack comes 10 days before Iraqis are scheduled to vote in a referendum on a new constitution, and concerns are high about a possible upsurge in violence.

Earlier, parliament, under international pressure, voted to reverse controversial new election rules that Shi'ite and Kurdish legislators were accused of passing to ensure the document's success.

Also Wednesday, a video dated September 12 was posted on the Internet and attributed to the Ansar al-Sunna militant group. It showed the apparent beheading of what the group claimed were two Iraqis who spied for the U.S. military.

Some information for this report provided by AFP and Reuters.