Iraqi police say a female suicide bomber has killed more than 40 Shi'ite pilgrims and wounded more than 100 others in Baghdad. For several years, sectarian violence has plagued the pilgrimage that marks the death of a revered Shi'ite figure.
Iraqi authorities say the bomber joined the pilgrims as they walked through a Shi'ite neighborhood in the capital.
The dead and wounded were among the hundreds of thousands of Shi'ites from Iraq, Iran and elsewhere in the region who make the journey to Karbala, 80 kilometers south of Baghdad, to mark the end of a religious mourning period.
The pilgrimage, banned under U.S.-ousted leader Saddam Hussein, a Sunni, has been hit by violence each year since it resumed.
Monday's attack follows several coordinated car bombings in Baghdad that have claimed hundreds of lives. Those explosions have been outside government buildings and hotels popular with foreigners.
Security analysts have tied the increase in violence to elections for parliament planned for March.
American University in Cairo Professor Abdullah al-Ashaal believes the attacks are also linked to the movement of U.S. troops.
"If you want to trace exactly who is making all that noise in Iraq, it is related very closely to the plans of the United States to withdraw from Iraq," he said.
The political science professor believes various forces, including Iran, are jockeying to fill the vacuum the withdrawal may leave. Sunni insurgents have also targeted the Shi'ite-dominated government.
U.S. forces left Iraqi cities in the middle of last year, just before the latest series of coordinated bombings began. The United States hopes to pull tens of thousands more troops from the country in the coming months.