Iraqi authorities set up new checkpoints and warned innkeepers to watch for suspicious people - all part of security measures to protect Shi'ites marking the holiest day of their calendar this week.
The measures were put in place Sunday ahead of the feast of Ashura to prevent a repeat of suicide bombings by al-Qaida in Iraq that killed at least 230 people during the past two years' ceremonies.
Sunni extremists have targeted the past two Ashura festivals. Eight suicide bombers killed 55 Shiites last year. In 2004, at least 181 people died in bombings at Shiite shrines in Baghdad and Karbala.
In Karbala, the center of the Ashoura commemorations, police warned innkeepers not to rent rooms to guests without proper identification. About 8,000 troops will be on duty in Karbala, officials said, and extra checkpoints have been set up on highways to protect Shi'ite pilgrims.