BAGHDAD - Hundreds of thousands of frenzied Shiites beat their heads and chests in unison and whipped themselves with chains Saturday across Iraq to honor the martyrdom of one of their most revered saints.
The processions were marred by violence with a deadly bombing in northern Iraq and clashes south of Baghdad.
The street battles between members of a messianic cult and Iraqi troops raged for a second day as the death toll from the fighting in two predominantly Shiite southern cities rose to at least 68.
Iraqi authorities say at least 36 people were reported killed in Basra, Iraq's second largest city, and at least 32 in Nasiriyah.
Video footage broadcast on Iraqi state TV showed several dead or injured men lying on bloodstained streets in Basra, where officials say the situation was under control.
There were conflicting accounts about how the clashes erupted, but all signs pointed to the radical Shiite group, which last year mounted a ferocious attack after Iraqi security forces raided its stronghold near the holy city of Najaf. The raid was meant to foil an alleged plot to slaughter pilgrims and leading clerics during Ashoura.
The group's bloody aims are seen as a bid to bring the return of the "Hidden Imam" - also known as the Mahdi - a descendant of the Prophet Muhammad who disappeared as a child in the ninth century. Shiites believe he will return one day to bring justice to Earth.
Nine blindfolded detainees sat hunched over on a curb as men held a sign behind them that said "criminal investigation department in Basra."
Clashes were ongoing in Nasiriyah, 320 kilometres southeast of Baghdad, as police fought gunmen holed up in buildings. Authorities, who spoke on condition of anonymity because of security concerns, said several senior police officers were among the dead.
Both cities are in provinces that have been handed over to the Iraqis and the clashes posed a major test for the Iraqi forces as they prepare to take over their own security so U.S.-led forces can go home.
The clashes in southern Iraq, where Shiites are engaged in a violent power struggle, also were a reminder of persistent divisions within Iraq's majority Islamic community at a time when the Pentagon is claiming some success in calming armed opposition among the Sunnis.
U.S. military spokesman Maj. Brad Leighton said jet fighters flew over the area in a show of force after the Iraqi's requested help, but said no airstrikes were carried out and the only U.S. involvement was the air support.
The assaults were launched as hundreds of thousands of Shiites observed the Ashoura holiday by marching, singing and beating their chests to honor the martyrdom of their most beloved saint, Imam Hussein, who was killed in a seventh century battle in the area.
Followers of the cult - the Soldiers of Heaven - seek to speed the return of another Shiite figure known as a "Hidden Imam," who believers say will bring justice to the world.
A series of recent high-profile attacks is eroding the security gains of the previous six months, when violence dropped across much of the country. The main insurgent group, al Qaeda in Iraq, has carried out many of the attacks against fellow Sunnis who have turned against it. But insurgents also struck with deadly suicide blasts this week against Shiites observing Ashoura.
Two bombs hidden under trash struck an Ashoura procession in the northern Iraqi city of Kirkuk on Saturday, killing at least two marchers and wounding five, police Brig. Gen. Burhan Tayeb Taha said.
Kirkuk, 290 kilometres north of Baghdad, has seen a rise in violence as militants have fled security operations elsewhere and ethnic tensions rise over the status of the oil-rich city.
