Iraqi security forces are on high alert Saturday as thousands of Shi'ite pilgrims gather in Baghdad for Sunday's commemoration of the death of an eighth century imam.
A vehicle ban is in force in the capital and some areas of the city have been sealed off to protect the pilgrims from terror attacks.
Media reports say militiamen of the Mehdi Army, loyal to the radical Shi'ite cleric Moqtada al-Sadr, are patrolling roads taken by Shi'ite worshippers into the city.
Experts say with hundreds of thousands of pilgrims arriving in Baghdad, it may be impossible to completely protect the festival.
Police say gunmen killed seven pilgrims in Baghdad late Friday.
Last year, nearly 1,000 pilgrims died when rumors of a suicide bomber triggered a stampede on a bridge across the Tigris River.
The Iraqi government imposed the vehicle ban on Friday. It will last until Monday morning (0200 UTC).
The ceremonies are taking place as American and Iraqi forces are conducting a large security operation in the Iraqi capital aimed at curbing sectarian violence threatening to plunge the nation into civil war.
Some information for this report provided by AFP and Reuters.