HILLA, IRAQ— Hundreds of thousands of Shi'ite pilgrims marked the end of the Arbaeen ceremony on Thursday in Iraq's holy Shi'ite city of Kerbala.
But violence has marred the week, a suicide car bomber killed at least 20 Shi'ite Muslim pilgrims in the Iraqi town of Mussayab on Thursday, during the peak of a Shi'ite religious rite, police said.
Mussayab is located some 60 kilometers south of the capital, Baghdad.
Arbaeen marks the end of a 40-day mourning period for Imam Hussein, a grandson of the Prophet Mohammad and a central figure of Shi'ite Islam who was killed in a seventh century battle. His followers believe he was buried in Kerbala.
Pilgrims attending the ceremony in the golden temple of the Imam Hussein beat their heads and chests whilst singing.
Snipers and bomb squads were among around 30,000 Iraqi police and soldiers deployed around Kerbala to watch over millions of pilgrims gathered to observe Arbaeen.
Shi'ites have been travelling by foot to observe the annual rite which is a major test for Iraqi security forces after a series of attacks targeted Shi'ite pilgrims across Iraq.
Shi'ite religious rites were banned under the rule of Saddam Hussein, who was ousted in 2003 by a U.S.-led invasion that triggered years of sectarian violence.
Explosions across Iraq killed at least 23 people and wounded 87 on Monday, police said, amid a growing political crisis that is inflaming sectarian tensions.
The pilgrimage site has been a repeated target of militants since the U.S.-led invasion that ousted Sunni dictator Saddam Hussein.
Last year, a suicide bomber disguised as a policeman killed at least 53 people and wounded scores in an attack on pilgrims at the end of Arbaeen.
Hussein, a Sunni, placed strict limits on pilgrimages to Kerbala, but since his overthrow in 2003, these have become a show of strength for Iraq's Shi'ite majority and a prime target of Sunni Islamist insurgents.
Meanwhile Iraq's Shi'ite prime minister, Nuri al-Maliki, on Monday warned he will not tolerate Sunni anti-government rallies indefinitely, but made a concession to their demands by promising to free some women prisoners.
Thousands of Sunnis have been taking to the streets of Iraq for more than a week in protest against Maliki, whom they accuse of discriminating against their sect and being under the sway of their non-Arab Shi'ite neighbor Iran.
The incident has once more threatened to plunge a delicate power-sharing deal into turmoil, just as President Jalal Talabani, a moderating influence, is in Germany for medical care after suffering a stroke.