A car bomb struck Shiite pilgrims boarding minibuses Saturday in Baghdad, killing at least six people, officials said, as extremists targeted travelers en route to the holy city of Karbala for the third consecutive day.
The explosives-laden car blew up about 9 a.m. near minibuses assembled to pick up pilgrims in Baghdad's mainly Shiite district of Shaab.
It was the latest in a series of bombings targeting Shiites heading to Karbala for a major religious festival that culminates this weekend. The deadliest was a female suicide bombing on Thursday that killed at least 18 pilgrims resting on the side of the road south of Baghdad.
A passenger van packed with explosives also blew up Friday night at a bus station in Balad, north of Baghdad where Shiite pilgrims had stopped for the night, killing four people and wounding dozens, U.S. and Iraqi officials said.
The attacks have raised concern that extremists were seeking to re-ignite the firestorm of sectarian massacres that plunged Iraq to the brink of civil war two years ago before thousands of American reinforcements were rushed to the country.
U.S.-backed Iraqi troops have stepped up security measures for the pilgrimage, but travelers remain vulnerable on the road.
In Karbala, pilgrims filed through metal gates to be searched before approaching the city's golden domed mosques. Women in flowing black robes were searched by female guards at a separate checkpoint from the men.
AP Television News video showed Iraqi security forces picking through plastic bags as men in T-shirts waited patiently.
Posters of Shiite religious leaders were confiscated for fear they might provoke attacks by followers of rival clerics, and cell phones that could be used to trigger bombs were banned.
A no-fly zone was enforced over the city, while police cars and ambulances roamed the streets. City officials set up dozens of tents around the city to provide food, water and emergency medical care.
Dozens of army and police snipers could be seen on buildings throughout the city looking for signs of trouble.
The Shiite festival, Shabaniyah, celebrates the birth of Mohammed al-Mahdi, the 12th Shiite imam, who disappeared in the ninth century. Devout Shiites call him the Hidden Imam and believe he will return to restore peace and harmony.
No group has claimed responsibility for the pilgrim attacks. Attacks on Shiite civilians — especially during Shiite religious festivals — have been the hallmark of Sunni extremists, including al-Qaida in Iraq.
Last year, Shabaniyah celebrations were tarnished when armed clashes broke out between followers of anti-American cleric Muqtada al-Sadr and security forces controlled by rival Shiite groups.
Soon afterward, al-Sadr declared a cease-fire, in large part because of the backlash provoked among Shiites by his followers' role in the Shabaniyah clashes.