At least 28 women and six men were killed when militants stormed several apartments in the Zayona residential complexes in eastern Baghdad, security officials told CNN.
The militants, wearing military uniforms and street clothes, fired their weapons in the streets before breaking down doors to enter the buildings on Saturday, security officials and residents told CNN. Once inside, they killed the men and women, the officials said.
Residents told CNN the Shiite Asa'b Ahl al-Haq organization carried out the attack. But the organization told CNN it does not have forces inside the city.
In other violence in Iraq, militants believed to be with the Islamic State in Iraq and Syria attacked the city of Haditha from four directions, said Hameed Ahmed al-Hashim, a member of the Anbar provisional council, and two security officials in Haditha.
A large military force backed by tribesmen defended the city, they said.
Iraqi jet fighters bombed a bridge controlled by militants east of Falluja, causing structural damage, al-Hashim said.
Three police officers were wounded when a roadside bomb exploded near their convoy in Kirkuk, a security official told CNN on Saturday.