The deadly Christmas Eve ambush of a Christian bus driver in Iraq Thursday and a bombing earlier this week targeting a 1,200-year-old church are driving Iraq's few remaining Christians quietly underground in the hours before the holy day begins.

Christmas has bumped into Shiite Islam's most mournful ceremony this year, forcing Iraqi Christians to shutter their homes and hide the signs of their celebration.

Midnight Mass will again be observed 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.

Unidentified gunmen ambushed a Christian man in Mosul on Thursday, shooting him after pulling him from the bus he was driving, police said. It was not clear if the attack was religiously based but it has put residents of the city on high alert.

That shooting came on the heels of a deadlier attack Wednesday, when a bomb hidden in sacks of flour exploded outside a historic church in Mosul, killing two people and wounding five.

"Instead of performing Christmas Mass in this church, we will be busy removing rubble and debris," said Hazim Ragheed, a priest at the Mar Toma Church.

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. And wary Christians across the country are responding by toning down their Christmas glitz.

"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, 50 miles south of Baghdad. The lunar Islamic calendar varies against the West's, and this year Ashoura happens to climax on Dec. 27.

Some 1.25 million Christians, 80 percent of them Catholic, used to live in Iraq. An exodus that began after the 1991 Gulf War, when Saddam Hussein imposed more Islamic policies, intensified after 2003, when Christians became targets of sectarian violence, and some 868,000 are left.

Iraq's top Catholic prelate, Chaldean Cardinal Emmanuel III Delly, said he used to hold Mass at midnight on Christmas Eve but in recent years switched the services to daylight hours, when the streets are safer.

"We will do our religious rituals as usual and on its dates, and our Muslim brothers will feel happy that each one has his own dear religion," Delly told The Associated Press.

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."

The Defense Ministry said patrols will be stepped up around churches, Christian neighborhoods and places of celebration, mostly in Baghdad, Mosul and Kirkuk. But that didn't prevent the deadly attacks in Mosul this week.

Christians aren't the only imperiled worshippers. Two dozen Shiite pilgrims preparing for Ashoura rituals were killed over the last two days in bombings in Baghdad and Hillah, about 60 miles to the south. Earlier this week, in Baqouba, two Shiites were gunned down while leaving a mosque where they had been flogging themselves for Ashoura. It was not known if they were targeted because of their beliefs.

Adnan al-Sudani, a cleric in the Shiite-dominated Sadr City neighborhood of Baghdad, said Christmas generates no ill will among his followers.

"We as Shiites respect Christian occasions and share their happiness in our hearts," he said.

Shiite shop owner Ali Qassim wished more people would have themselves a very merry Christmas. His electronics shop, in the mixed Muslim-Christian neighborhood of Karrada, is packed with artificial pine trees and cherry-cheeked faces of plastic Santas, called Baba Noel in Arabic.

But few were sold.

"Nothing is in the streets. Nothing is in the shops," said Qassim, looking out on the bustling midday traffic. "In the past, fashion stores used to put up Baba Noel and a tree in front of the shop. But out of respect, many families will not celebrate because of the Ashoura and to sympathize.

"I miss it."

The Associated Press contributed to this report.