BAGHDAD - Bombs targeted Iraqi Christians and Shiite Muslims yesterday, killing at least eight people and wounding four dozen before coinciding religious observances that will take place under heavy guard.

Insurgents have routinely targeted Shiites and Christians in an attempt to undermine the country's security gains and its Shiite-dominated government. Security forces in recent days have been concerned that the Shiite holy observances known as Ashoura and Christmas gatherings would be targeted by large-scale attacks.

Ashoura marks the seventh-century death of the prophet Muhammad's grandson Hussein.

In the first of yesterday's attacks, a bomb targeted a historic church in the northern city of Mosul a day before Christmas Eve services, killing two people and wounding five.

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

The bomb was hidden under sacks of baking flour in a handcart left 15 yards from the Mar Toma Church, or the Church of St. Thomas, a police officer said.

The officer said the two men killed were Muslims and that five other people were injured. A hospital official confirmed the casualties. The officials spoke on condition of anonymity.

The blast damaged the wooden doors, windows, some furniture, and one of the walls of the church, which is more than 1,200 years old, Ragheed said. Services will be moved out of the church, but Ragheed did not say where they would be held.

"We demand that the government put an end to these repeated attacks," Ragheed said.

The blast occurred in an area where streets have been closed to cars and trucks to protect Mosul's dwindling Christian population.

Iraqi defense officials warned earlier in the week that intelligence reports pointed to attacks during Christmas, leading the government to step up security near churches and Christian neighborhoods.

Most of the increased security will be in Baghdad, Mosul, and Kirkuk, said Defense Ministry spokesman Maj. Gen. Mohammed al-Askari.

Later yesterday, a blast struck a group of Shiite pilgrims preparing for Ashoura in Baghdad. The bomb, hidden in a bag, killed four pilgrims and wounded 31 others in eastern Baghdad, a police officer said. Among the wounded were women and children, he said, speaking on condition of anonymity.

A second blast struck Shiite worshipers gathering in central Baghdad. The bomb, hidden behind a tent erected to provide food and water to pilgrims, killed one pilgrim and wounded four others, said another police official.

A third blast in western Baghdad killed one pilgrim and wounded eight others who had gathered to prepare for Ashoura rituals, police said.