The U.S. military says violence in the Iraqi capital has increased 22 percent in the first three weeks of the Muslim holy month of Ramadan.
A U.S. military spokesman, Major-General William Caldwell said a highly-touted security operation in Baghdad is under review given what the spokesman described as its "disheartening results."
The mounting casualties have intensified pressure on Iraqi government to find ways to stem the country's surging sectarian violence.
On Wednesday, Prime Minister Nouri al-Maliki met with Iraq's top two Shi'ite clerics. They condemned the violence, but no one has produced any specific plans on how to improve security in the country.
Iraqi police say a string of bombings and suicide attacks Thursday killed more than 40 people across the country.
Police say a bomb blast in the town of Khalis, north of Baghdad, killed at least 10 people and wounded more than 20 others, while suicide attacks in the northern cities of Kirkuk and Mosul killed at least 23.
Fighting also erupted in several locations across Baghdad, killing at least eight people, including four policemen.
The U.S. military said 13 American troops were killed on Tuesday and Wednesday in Iraq, 71 this month alone.