Shiites in their hundreds of thousands crowded the streets of Karbala on Tuesday, many beating their own backs with metal chains as the annual Ashura ceremonies began building towards a peak.
The shrine city south of Baghdad was heavily guarded as devotees from across the Muslim world flooded through security checkpoints to reach two imposing shrines - one to Imam Hussein, the other to his half-brother Imam Abbas.
The rituals - commemorating the killing of Imam Hussein by armies of the Sunni caliph Yazid in 680 -- will reach their climax in Karbala on Wednesday, but processions marking Shiite Islam's holiest days have been held across Iraq for the past week.
Around two million people are expected to be in Karbala, 100 kilometres (62 miles) south of Baghdad, by Tuesday, guarded by a heavy security force deployment.
"More than 28,000 security forces including back up troops from the interior ministry (police) in Baghdad were sent to control the security of the city," military commander Brigadier General Othman Qanimi said earlier this week.
Huge numbers of jumpy police patrolled the streets while at checkpoints near the centre of the city pilgrims were subject to intensive searches. Above, helicopters were seen crisscrossing the sky.
Akil al-Khazali, governor of Karbala province, said more than 55,000 foreigners had already arrived from countries such as Iran, Bahrain, Saudi Arabia, Kuwait, Oman, Pakistan and Tanzania.
Swarming crowds in Karbala on Tuesday joined sombre processions in which men and even some boys, accompanied by drummers, beat their chests and engaged in the devotional self-flagellation that characterises the Ashura rituals.
Tradition holds that Hussein was decapitated and his body mutilated by Yazid's armies.
To express remorse and guilt for not saving Hussein, Shiite volunteers flay themselves with chains or slice their scalps during processions to the two shrines.
Tents and small wooden rooms covered in black fabric and adorned with lights and pictures of Shiite imams have sprung up across the city for pilgrims in need of food or seeking a rest from the intense bustle of the streets.
The pilgrims ritually drink a goblet of fresh water to remember the burning thirst that 71 family members of Imam Hussein endured as they were led through the desert to captivity in Syria.
Participating in the Ashura commemorations in Karbala is for Shiite Muslims second only to the pilgrimage to Mecca in Saudi Arabia.
"I dreamed since my childhood of seeing Karbala, and now my childhood dream has come true," said Kossid Akhour, 50, a pilgrim from Pakistan dressed in black robes, the colour of mourning.
His friend Assim Abbas, 25, described his visit to Karbala as arriving in the "paradise" he had always dreamed of.
Many pilgrims crossed the border from Iran, which has the largest concentration of Shiite Muslims in the world.
"Being near the Imam Hussein shrine on Ashura is the most important thing in my life," said Iranian Sadiq Hussein, 40, sporting a green bandana that represents the colours of the Prophet Mohammed.
Medical tents have also been set up to take care of pilgrims that get too carried away in the ritual flaggelations.
"I'm not afraid to hit myself vigorously," said Fulayah Hassani, 34, said, his head freshly shaven so he could better see the wounds he will make on his forehead with a knife.
But pilgrims shrugged off security fears, which have been heightened by attacks in recent days by Sunni insurgents against devotees participating in Ashura rituals despite much-improved security across the country.
On Sunday, a female suicide bomber blew herself up in the middle of pilgrims queuing at security gates leading to an important shrine in Baghdad, killing at least 35 people and wounding dozens.
Kolam Abbas, a tour guide from Madagascar who was on his fourth visit to Karbala, said that he was willing to take the risk.
"The circumstances in the city have changed, I feel more secure today," he said.
Blair blasts Britons over Iraq war