The emotional event commemorates the 7th century battlefield martyrdom of Hussein, whom Shiites view as the rightful successor to the Prophet Mohammed, the issue at the heart of a schism with Sunni Islam.

To mourn his death in the year 680, Shiite worshippers wearing black cry and beat their chests in unison and some flagellate themselves with swords and knife-edged chains.

Shiites represent more than 10 percent of the world's 1.8 billion Muslims, and Ashura is marked by millions of people from Afghanistan and Pakistan to Iran and Lebanon.

Hussein lies entombed in a golden-domed mausoleum in Karbala, where he was killed by the Sunni troops. His mausoleum is linked to that of his brother Abbas, who also died in the battle.

This year's festivities, which began on Monday evening, come as Iraq's majority Shiite population is split between rival political camps.

Backers of the influential cleric Moqtada Sadr were continuing a sit-in outside parliament in Baghdad for a 10th day on Tuesday.

They oppose the Coordination Framework, an alliance of pro-Iran Shiite factions that has tried to appoint a prime minister against Sadr's wishes.

"The Shiite house is divided," said Yussef al-Ardawi, 50, an employee of the Abbas Mausoleum. "We didn't expect this from Shiite politicians."

Another worshipper, 24-year-old medical laboratory worker Hussein from Nasiriyah in the south, said the tensions come as Iraqis face a litany of problems.

"We are in 2022 and we don't even have electricity," he said about the oil-rich but corruption-plagued country now enduring blistering summer heat.

"Imam Hussein rose up against injustice, against oppressive power," he said. "All the people should rise up."