Terrorists in Iraq used car bombs to target Shiite religious processions Wednesday, killing at least 66 people.

The 16 explosions across five Iraqi cities were the third this week targeting the annual Shiite pilgrimage that culminates on Saturday.

Hundreds of people were wounded in Wednesday's blasts, and the death toll is expected to climb.

The first bomb struck a procession at around 5 a.m. in the town of Taji, north of Baghdad. That was followed by four more morning blasts across the capital.

By early afternoon, all of the 16 separate, coordinated attacks had been carried out.

Most of the explosions targeted Shiite pilgrims, but two hit offices of political parties linked to Iraq's Kurdish minority.

Iraq's political divide has deepened since the U.S. troop withdrawal. Shiite Prime Minister Nouri al-Maliki has been accused of trying to monopolize power, and Sunni Vice President Tariq al-Hashemi was recently charged with running death squads.

"These violent acts reflect the depth of the political crisis in the country and the escalation of political differences among blocs," Sunni politician Abdul-Sataar al-Jumaili said.

Authorities have tightened security as the Shiite pilgrimage continues