Witnesses said the suicide bomber, wearing an explosives vest, tried to gain access to the offices of the Iraqi Unity Gathering, a non-governmental group hosting an Army Day event for officers, most of whom attended in civilian clothes.
Iraqi government and hospital officials said six of the dead were members of the security forces. Seven other police and soldiers were wounded, along with 10 civilians.
Lieutenant Steven Stover, a US military spokesman, cited witnesses as saying that two Iraqi soldiers were killed when they hurled themselves on to the attacker as he detonated his explosives.
"They absorbed some of the blast. They saved a lot of lives," he said.
Stover said in a later statement: "The selfless sacrifice of the two Iraqi [soldiers] should not be forgotten. These two Iraqi martyrs gave their lives so that others might live."
Army Day marks the 87th anniversary of the formation of the first Iraqi army regiment.
Tribal leaders from both of Iraq's religious sects and clerics were present at Sunday's ceremony, held in a house in a residential neighbourhood in Karrada district.
|Iraqi soldiers were dancing in the streets |
just before the bomber struck [Reuters]
Reuters television footage showed a group of soldiers dancing in a tight circle in the street, waving their AK-47 assault rifles in the air and chanting "Where is terrorism today?" just minutes before the bomber struck.
The bomber attacked as people were leaving the venue of the celebrations and milling about outside.
Security force members who had been standing guard appeared to have taken the brunt of the blast.
Police in Baghdad said three more people were killed on Sunday in the northern Baghdad district of Qahira when a car bomb blew up outside a restaurant.
One other person was killed in three blasts in central Nahda.
Police also said the leader of the Awakening Council in Baghdad's Shaab district was shot dead outside his home on Sunday.
Separately, police reported the discovery of 12 bodies around Baghdad on Saturday.
Such killings are normally associated with sectarian death squads.
In the northern city of Mosul, three apparently co-ordinated explosions targeted two Christian churches and a convent, local officials and the US military said.
There were no deaths, but four people were wounded.
"They are cowards," a priest told The Associated Press, refusing to give his name because he feared for his safety. "We don't know what message they want to convey."
"This act will only foster our insistence to remain loving brethren to all sects in the city. I'm sure that those who committed this crime are far away from religion."
The attacks began around 2pm in eastern Mosul when a parked car bomb exploded near a Chaldean Catholic church, causing damage but wounding no one.
About 30 minutes later, another parked car bomb exploded in the eastern part of the city near an Assyrian Christian church, damaging the building and wounding four passers-by.
At nearly the same moment, a bomb explosion near a Chaldean convent in western Mosul damaged the building and a few nearby houses but hurt no one.