Baghdad ? Bombers struck Shiite pilgrims Saturday for a third consecutive day, killing at least three people in the latest in a series of attacks apparently aimed at stoking sectarian tension.

The attacks have targeted pilgrims headed for the Shiite city of Karbala, where hundreds of thousands of people have gathered for festivities that will culminate this morning.

No group has claimed responsibility, but assaults on Shiite civilians have been carried out for years by Sunni extremists such as al-Qaida in Iraq.

The latest attack occurred about 9 a.m. Saturday when a car bomb exploded in the north Baghdad neighborhood of Shaab as pilgrims were boarding minibuses bound for Karbala, 50 miles to the south.

Iraqi police and hospital employees said six people were killed and 11 injured. The U.S. military put the toll at three dead and eight injured.