Iraqi police say they found 30 decapitated bodies on Sunday near the city of Baquba.
Authorities are working to identify the victims. The discovery is the latest since sectarian violence flared following the bombing of a Shi'ite shrine last month.
In Baghdad, Iraqi police say 18 followers of Shi'ite cleric Moqtada al-Sadr were killed in fighting with U.S. forces near a mosque. The U.S. army has not confirmed the clash.
Earlier on Sunday mortar shells landed near the cleric's home in Najaf, wounding two guards and a child.
And Iraqi authorities say US forces arrested 40 Iraqi security personnel after raiding a bunker where 17 foreigners were being held.
In other violence, a roadside bomb killed a teenage boy as he walked to school in Basra. A bomb in Baghdad killed a woman, and and gunmen killed two people, including a police officer near Baquba.
The attacks came as Iraq's Shi'ite, Sunni Arab and Kurdish leaders failed again to agree on a government, despite increasing U.S. pressure.
A delegation led by U.S. Senator John McCain met with Iraqi President Jalal Talabani and Prime Minister Ibrahim al-Jaafari Saturday and called for the stalemate to be resolved soon.