Over a million Shiites - some ritually flailing themselves, others slashing their heads with swords - have crowded into this holy city over the past few days for a festival mourning the martyred grandson of the Prophet Muhammad. 

Such pilgrimages had been tightly regulated for decades under Saddam Hussein - and practices like flailing were banned outright. But with Saddam's fall, it was a whole new day for Iraq's long-suffering Shiites. 

At the anti-American protest, Shiites carried banners with messages such as "No to America, no to Israel, yes to Islam." The demonstrators marched through the streets for an hour before dispersing. 

"Saddam Hussein was evil. And so is America," said Khudayer Abbas Musawi, a 25-year-old engineering student. "America came here not to free the Iraqi people but for oil. They came to occupy, not to liberate. The Americans removed Saddam and now the Americans should leave." 

Not everyone agreed. 

Kathem Jasim Mohammed, a 50-year-old vendor, said: "I want to thank Mr. Bush for breaking the prison in which Iraq was. I thank him for what he did and God bless him." 

Despite bitter internal differences, the Shiites, who represent 60 percent of Iraq's 24 million people, were able to pull off the pilgrimage on short notice and thus far without violence. 

At noon Wednesday, throngs of pilgrims began the final prayers of the pilgrimage, after which people were expected to begin leaving the city. Wednesday was the 40th and final day of the mourning period for Muhammad's grandson Hussein, who was killed in a power struggle 1,300 years ago. 

While U.S. officials estimated the crowd at a million, one Shiite spokesman insisted it was much higher. 

Abu Eslam al-Saqir, a spokesman of Supreme Council for the Islamic Revolution in Iraq, the biggest Iraqi opposition group, estimated the religious faithful at well over 4 million. 

"The huge gathering does carry a political and religious message for everybody, including the Americans," he said Wednesday, speaking from Tehran. "It means: Iraqis are standing on their soil and expressing what they love and what they want. People love Islam. However, no Islamic or U.S.-installed administration could be imposed on the Iraqi people. " 

After journeying in 90-degree heat to Karbala - the site of Hussein's tomb - many of the pilgrims slept in the streets and helped themselves to chicken and rice from huge communal pots. 

Shiites from Iran joined those from Iraq and other countries in converging on Karbala. But the Iranian presence appeared to be lower than in previous years, perhaps because many Iranians did not have time to make travel arrangements or were uncertain they would be able to get into Iraq. 

Thousands of Shiite volunteers managed security and traffic. American troops were ready with food and water - it was not needed - and treated scores of people suffering sprains, cramps and heat exhaustion. 

But for the most part, U.S. forces stayed clear of the city to avoid friction with the Shiite pilgrims. 

The U.S. military said police on Monday arrested six men who had been planning to blow up two of Karbala's mosques. Five of the men claimed to be members of Saddam's Baath Party, and one said he belonged to al-Qaida, said Army Capt. Jimmie Cummings. 

Shiites were long suppressed by Saddam's ruling Sunni minority. Since Saddam fell, Shiites have been setting up local administrations, and religious leaders have emerged as key sources of political power. 

The United States hopes to work with Shiites to form a new government without resorting to a Shiite theocracy like Iran's. 

Senior Shiite clerics insist they want to share power with Iraq's Sunnis and Kurds. But many Shiites, from secularists to fundamentalists, distrust the United States.