BAGHDAD (AP) -- Processions of black-clad men flagellating themselves with chains to express grief at the martyrdom of Imam Hussein marched Tuesday through the city of Karbala, as a national pilgrimage marred by deadly attacks neared its conclusion.

Shiites from all over Iraq have walked to Karbala, about 80 kilometers south of Baghdad for Arbaeen. The commemoration marks the end the mourning period following the anniversary of the martyrdom of Imam Hussein, who was martyred in a seventh century battle and is buried in Karbala.
Iraqi authorities have said at least eight million pilgrims are expected to swell the streets of the city by the time the time ceremonies reach their peak on Wednesday and Thursday.
With heavy security in the city, extremists have struck in recent days at more-exposed pilgrims on their way to Karbala. At least 63 pilgrims have been killed.
Police Chief Raid Shakir Jawdat has said 40,000 police officers and military troops are being deployed to prevent attacks, with patrols on the outskirts of the city guarding against rocket or mortar attacks and hundreds of snipers on tall buildings.
The United States blamed al-Qaeda in Iraq on Monday for the sectarian attacks, the worst of which killed 56 and wounded scores of pilgrims who were taking a break from their travels Sunday at a refreshment tent.