Iraqi police say U.S. and Iraqi forces have killed more than 250 insurgents in a day-long battle near the Shi'ite holy city of Najaf.
The U.S. military says two American troops were killed Sunday when a U.S. helicopter crashed while helping Iraqi forces during the battle. The military did not say how the helicopter went down.
The Iraqi military says at least 10 insurgents were captured.
Iraqi sources say the raid was launched while insurgents were planning to attack Shi'ite clerics during this week's Ashura observances in Karbala, between Najaf and Baghdad.
In other news, Iraqi officials say attacks in Baghdad killed at least 15 people, and car bombs in Kirkuk, in northern Iraq, killed another 16.
The U.S. military also announced three other American combat deaths in Iraq.
Thousands of Iraqi soldiers and police are deploying around Karbala to provide security for Shi'ite pilgrims during Ashura.
Ashura marks the seventh century slaying of the Shi'ite Imam Hussein, grandson of the Prophet Muhammad, at Karbala. Shi'ites believe Hussein was the prophet's heir. Hussein's death solidified Islam's split into rival Sunni and Shi'ite branches.
Karbala's governor says Iraqi forces have begun blocking roads to prevent car bombs from reaching the city.
Some information for this report was provided by AFP, AP and Reuters.