At least 23 people were killed and dozens were wounded Monday when two car bombs, including one driven by a suicide attacker, blew up in Baghdad, police said.

Neither of the attacks took place in parts of the sprawling city where visiting Iranian President Mahmoud Ahmadinejad was located.

In an unrelated incident, the U.S. military reported finding a grave containing 14 people, believed to be members of the Iraqi security forces and thought to have been executed by Al Qaeda in Iraq.

In the deadlier of the two attacks in Baghdad, a parked car bomb killed at least 21 people and wounded 43 in central Baghdad's Bab al-Mudham area. The car was parked on a road leading to the nearby Housing and Municipality Ministry, police said. The dead included one police officer, while another four were wounded. The district is a commercial area on the eastern side of the Tigris River.

The U.S. military confirmed there was a car bombing but was investigating the incident and could not immediately provide more details.

In the suicide attack, a man drove a minibus into the headquarters of the Interior Ministry's 4th Brigade, a special quick reaction force based in Baghdad's eastern Zayouna neighborhood. The blast killed at least two police officers and wounded six other people. Associated Press images taken after the blast showed massive damage to homes in the neighborhood.

Authorities who provided details of both bombings spoke on condition of anonymity as they were not authorized to release the information.

The U.S. military said its soldiers discovered 14 bodies on Sunday in a mass grave south of the city of Samarra, located about 60 miles north of Baghdad.

The military said all the victims had their hands tied behind their backs and had been shot in the head — execution style.

"Coalition and Iraqi forces believe Al Qaeda in Iraq is responsible for these murders. The victims are believed to have been members of Iraqi security forces or Sons of Iraq," a military announcement said. Sons of Iraq is a phrase often used to describe U.S.-funded Sunni tribesman who are now fighting Al Qaeda.

Many Sunnis in the area and around Iraq have switched allegiances and now fight for the United States because of the tactics used by the extremist group. Lt. Col. Thomas Hauerwas, executive officer of the 1st Brigade Combat Team, 101st Airborne Division, said people in the area were "standing up to Al Qaeda throughout the province because of this and other atrocities committed against innocent people."

The military also said Monday that a car bomb in Samarra had on Sunday killed four people, including one child. Police in Samarra reported that at least seven people were killed and 10 people were injured in Sunday's car bomb.

The U.S. military accused Al Qaeda in Iraq of being behind Sunday's bombing.

In yet another attack on Monday, police reported that three officers were killed by a parked in the town of Shikaat, north of Baghdad.