The U.S. Embassy in Iraq condemned the "deliberate and senseless" targeting of Christians after three bombs killed 37 people in the capital Baghdad on Wednesday.
At least 26 people died and 38 were injured after a bomb went off near a church in the southern neighborhood of Dora, a police officer told The Associated Press.
Earlier in the day, two bombs went off in a market in the Christian area of Athorien, killing 11 and wounding 21, the officer said.
"The United States Embassy condemns in the strongest terms today's attacks in the Dora area of Baghdad that targeted Christians celebrating Christmas," an embassy statement said. "The Christian community in Iraq has suffered deliberate and senseless targeting by terrorists for many years, as have many other innocent Iraqis.
"The United States abhors all such attacks and is committed to its partnership with the Government of Iraq to combat the scourge of terrorism.
"We extend condolences to the victims and their families and wish a rapid recovery for those who were injured."
The bomb in Dora went off after Christian Mass but none of the worshipers were hurt, according to Iraq-based leader of the Chaldean Catholic Church, Louis Sako.
He told the AP he did not think the church was the target.
No one immediately claimed responsibility for the attacks. The AP reported that Iraq's dwindling Christian community, which is estimated to number about 400,000 to 600,000 people, has often been targeted by al Qaeda and other insurgents who see the Christians as unbelievers.
A medical official confirmed the casualty figures to the AP. Both officials spoke on condition of anonymity because they are not authorized to talk to the media.
Wednesday's bombings came amid a massive military operation in Iraq's western desert as authorities try to hunt down insurgents who have stepped up attacks across Iraq in the past months, sending violence to levels not seen since 2008.
The Christmas Day attacks brought the total number of people killed so far this month in Iraq to 441. According to U.N. estimates, more than 8,000 people have been killed since the start of the year.
The Associated Press contributed to this report.
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