Christmas is bumping into Shiite Islam's most mournful ceremony this year, forcing Iraqi Christians to keep their celebrations under tighter wraps than usual.

Midnight Mass will again be celebrated in daylight across Baghdad, and security around churches is heavier for a community that's been threatened by sectarian violence since the 2003 U.S.-led invasion. A deadly Christmas Eve ambush of a Christian bus driver Thursday and a bombing earlier this week targeting a 1,200-year-old church, both in Mosul, underscored their concerns.

But this year, Christians feeling an extra need for caution are toning down the Christmas glitz, and the plastic Santas aren't selling as well as usual. At least one Catholic archbishop has discouraged Christmas decorations and public merrymaking out of respect for Ashoura, a period of Shiite mourning and self-flagellation.

"We used to put the Christmas tree with its bright lights close to the window in the entrance of our home," said Saad Matti, a 51-year-old surgeon and Basra city councilman.

"But this year, we put it away from the window as a kind of respect for the feelings of Shiite Muslims in our neighborhood because of Ashoura," he said.

Ashoura caps a 10-day period of self-flagellation and mourning for the Prophet Muhammad's grandson, Imam Hussein, killed in 680 A.D. during a battle that sealed the split between Shiites and Sunnis.

During the 10 days, throngs of Shiite pilgrims march to the holy Iraqi city of Karbala, 80 kilometers (50 miles) south of Baghdad. The lunar Islamic calendar varies against the West's, and this year Ashoura happens to climax on Dec. 27.

Shiites are the majority of Iraq's 28.9 million people and now dominate the country politically, giving other sects more reason to accommodate them.

Few weddings are held during Ashoura, and any business associated with beauty _ flower shops, jewelry stores, photography studios _ loses money.

"No weddings, no work," Nijood Hassan, a Sunni, complained at her flower shop central Baghdad. "Why do they have to do this?"

But the compulsion to preserve an outward appearance of harmony is strong. Hassan's sister, Nadia, quickly interjected: "There is no sectarian division any more, and we have no objection whatsoever about that."

The archbishop of the southern Shiite-dominated city of Basra, Imad al-Banna, called on Christians "to respect the feelings of Muslims during Ashoura and not hold the public celebrations during Christmas. ... to hold Mass in the church only and not receive guests or show joyful appearances."