Iraqi authorities banned motorcycles from Baghdad’s streets and dispatched tens of thousands of security forces to guard a Shiite pilgrimage yesterday after coordinated car bombings targeted processions across the country the day before, killing 72 people in one of the worst attacks since the US troops withdrawal.

Despite the violence, hundreds of thousands of faithful Shiites continued their marches to commemorate a revered saint.

The processions of pilgrims carrying green banners filled roads into and around the capital as they made their way toward the twin-domed shrine in Baghdad’s Kazimiyah neighborhood where Imam Moussa Al-Kadhim is said to be buried.

“The events that took place yesterday will never undermine our determination to go to commemorate Imam Al-Kadhim,” vowed pilgrim Sayid Ali Jassim, standing near a security checkpoint where heavily armed soldiers peered out from behind barriers.

Main Baghdad streets were closed off with concrete blocks yesterday, and soldiers at roadblocks searched pilgrims as they entered roads leading to the shrine.

A senior Defense Ministry officer said motorcycles had been banned to reduce the risk that one might slip a bomb past a checkpoint, and he said at least 30,000 soldiers and police were on the streets. He spoke on condition of anonymity to discuss the measures.

Authorities yesterday raised the death toll to 72 and said the 22 explosions in seven cities and towns on Wednesday also wounded more than 270 people, according to two officials from the health and interior ministries.

The officials spoke on condition of anonymity because they were not authorized to talk to the media. The attacks around the country came amid political tension over power-sharing. Iraq’s Sunnis and Kurds accuse the Shiite prime minister, Nouri al-Maliki, of consolidating power in his own hands.

The sharpening political divisions suggest Iraq has made little progress in healing the breach among its religious and ethnic communities that once pushed the country to the brink of civil war.

No one has claimed responsibility for Wednesday’s attacks but the bombings bore the hallmarks of al-Qaeda and its Sunni militant allies seeking to exploit the sectarian tensions.

Iraqi authorities played down any suggestion that the devastating attacks that have taken place every few weeks or so since the US military withdrew in mid-December portend a return to the all-out, sectarian violence that tore the nation apart in 2006-2007.

Wednesday’s blasts were the third in a week targeting the annual Shiite pilgrimage to observe the eighth-century death of al-Kadhim, a revered saint who was the Prophet Muhammad’s great-grandson.

The commemoration culminates on Saturday. The level of violence has dropped dramatically in Iraq since the height of the war, though Shiite religious events still are often targeted.

But large-scale bombings still come once or twice a month and security forces have been unable to prevent such the attacks, even though they were on high alert this week.