Shiites from Iraq, Iran and other countries were converging on the city of Karbala - site of the 7th-century martyrdom of Hussein, a grandson of the Prophet Muhammad. The annual pilgrimage, which marks the anniversary of the end of the traditional 40-day mourning period, culminates Thursday. 

Brig. Gen. Vincent Brooks, deputy operations director at U.S. Central Command, said there were estimates of more than 1 million people participating. 

The presence of such a vast crowd of pilgrims from throughout the country attests to the power and the potential of the majority Shiite community, which was long repressed by Saddam's mostly Sunni Muslim government. 

The Shiites were able to set aside bitter internal differences for the rituals, which became a celebration of the new Shiite freedom. Shiites have been setting up local administrations to re-establish order, and religious leaders have emerged as key sources of political power, especially in southern Iraq. 

"It is a symbol of Shiite unity and their rejection of oppression and injustice," said Hamid al-Bayati, representative of the Iran-based Supreme Council for the Islamic Revolution in Iraq. 

"It's an expression of their yearning for freedom," he said from his London office. 

At least one leading Shiite figure has called for the Karbala gathering to be used as a protest against U.S. domination of Iraq, and some pilgrims in Karbala held anti-U.S. signs, including "Bush Saddam" and "Down USA." 

But Brooks, speaking in Qatar, noted that pilgrims were "participating in something that would not have been possible before. And thus far it has occurred without any significant incidents." 

In an apparent attempt to avoid any friction with the pilgrims, no American troops appeared in the city. At one of the entrances to Karbala, members of the Free Iraqi Forces, the military wing of the U.S.-backed Iraqi National Congress, were seen checking cars. Some of them wore black headbands, a symbol of mourning. 

The pilgrims included men and women of all ages - the men clad mostly in white robes and headbands, the women cloaked head to toe in traditional black dress. 

Despite the sadness of the occasion, the mood in the sacred city was exciting. 

Packs of men circled the city's main shrines, creating a vortex of humanity. Some worshippers carried photos of famous Shiite clerics. 

Two groups of 100 men in white robes slashed their heads with long, sharp swords, spraying blood on those near them, to symbolize their anguish over the slaying of Hussein. 

Hussein was killed in the Battle of Karbala between a small group of his followers and the Umayyad Army. The Shiites see Hussein and his father, Ali, as the rightful heirs to the prophet, and the battle in which Hussein was killed was one in a series of violent clashes between Sunnis, who disputed the Ali-Hussein claim, and Shiites. 

On Tuesday, Shiites waved their blades at Hussein's shrine, shouting, "Ya Hussein," or "Hail, Hussein," a way of declaring their readiness to sacrifice for Hussein. Some were taken away in cars to get medical treatment, others appeared later at a traditional Iraqi bathhouse. 

Inside the shrine, groups of the faithful beat their chests and screamed: 

"You dirty Saddam, where are you so that we can fight you?" 

Ahmed Abdel-Wahed, 28, of Baghdad, said, "He who dared to march ... used to disappear." Abdel-Wahed had just returned to Iraq from Jordan, where he fled two years ago out of fear of persecution. 

A portrait of Saddam that used to hang on the main Imam Hussein shrine was gone, underlining the new sense of freedom enjoyed by Iraqi Shiites. 

"People used to be detained if they were seen beating their chests near or inside the shrine," said Ouza Qateh, 42, who walked from Basra to Nasiriyah and then drove to Karbala to make the pilgrimage. 

The roads in the area were choked with pilgrims, some of them limping from long journeys. Two men crawled on their stomachs into one shrine; months back, they had vowed to crawl into Karbala if the Americans ousted Saddam. 

"We were prohibited from visiting these shrines for a long time by the Baath Party and their agents," Abed Ali Ghilani told Associated Press Television News in Karbala. "This year we thank God for ridding us of the dictator Saddam Hussein and for letting us visit these shrines." 

Water trucks were brought in to help the crowd - which already may have surpassed a million people - weather Tuesday's 90-degree heat and blazing sun. Roving men sprayed the worshippers with rose water, which cools and conveys a blessing. 

Saddam's regime had permitted the annual pilgrimages, but prohibited people from coming on foot or engaging in the ritual slashings, and monitored the participants as well as centers of Shiite rebellion in Najaf and Karbala. 

Despite their newfound freedoms, rifts have erupted among the Shiites since Saddam's fall. Abdul Majid al-Khoei, a cleric who had opposed Saddam's rule, was hacked to death April 10 in the holy city of Najaf along with a pro-Saddam cleric with whom he appeared as a gesture of reconciliation. 

Al-Jazeera television, which estimated that up to 2 million people were converging on Karbala, reported that some senior clerics did not show up Tuesday, possibly because of security concerns. They included the Grand Ayatollah Ali al-Sistani, Iraq's top Shiite cleric, and Muktada al-Sadr. 

Al-Sistani was one of several clerics reportedly threatened by the mob in Najaf, which was reportedly led by al-Sadr and made up of members of Saddam's Baath Party.