At least 24 people were killed and dozens were wounded Monday when two homicide car bombs exploded in different parts of Baghdad, police said.

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

Also Monday, the U.S. military reported finding a grave with 14 bodies, believed to be members of the Iraqi security forces executed by Al Qaeda in Iraq.

In Baghdad's deadliest attack, a homicide car bomber killed at least 22 people and wounded 43 in central Baghdad's Bab al-Mudham neighborhood on the eastern bank of the Tigris. Associated Press Television News footage showed a 6.5-foot crater blown into the street by the explosion, which destroyed numerous cars and trucks and littered the area with shrapnel and debris.

The figures provided by police and hospital officials differed significantly from those given by the U.S. military, which reported that nine people had died and seven were wounded from what it described as bomb in a vehicle. It was not immediately clear why the numbers were so different.

The bomber apparently was targeting a checkpoint manned by a neighborhood protection group. One police officer was among those killed and four were among the wounded.

There were initial reports that the bomb had been in a parked car, but Iraqi police later said it was a homicide attack.

In the other homicide bombing, a man drove a mini bus toward the headquarters of the Interior Ministry's 4th Brigade, a special rapid reaction force based in Baghdad's eastern Zayouna neighborhood. The blast killed at least two Iraqi soldiers and wounded five other people, the U.S. military said. Associated Press images showed massive damage to homes in the neighborhood.

Iraqi soldiers manning a checkpoint managed to prevent the minibus from entering the compound, the U.S. military said.

"A minibus laden with explosives was stopped by the heroic actions of several Iraqi Army soldiers manning a checkpoint," said Col. Allen Batschelet, the chief of staff for U.S. forces in Baghdad. "Without a doubt, had the suicide bomber reached his target, more lives would have been lost. The Iraqi Security Forces are proving themselves capable of protecting the Iraqi people and are daily showing their heroism against a common enemy."

U.S. soldiers discovered 14 bodies on Sunday in a mass grave south of the city of Samarra, about 60 miles north of Baghdad. The military said the victims had their hands tied behind their backs and had been shot in the head.

"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 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 a car bomb in Samarra on Sunday had killed four people, including one child. Police in Samarra, however, reported that at least seven people were killed and 10 people were injured.

The U.S. military accused Al Qaeda in Iraq of being behind the bombing.

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