The explosions which began after 6 pm hit four churches in Baghdad and one in Mosul. Eyewitnesses said they shattered windows and bloodstained members of the congregations were seen running out into the streets. A sixth bomb outside another Baghdad church was disarmed by the police.
Iraq's National Security Advisor Mowaffak al-Rubaie said the bombings bore the hallmarks of insurgent leader and Al Qaeda ally Abu Musab al-Zarqawi. He is thought to have personally decapitated US contractor Nick Berg and South Korean translator Kim Sun-il.
In other incidents, five people were killed and 53 hurt in a suicide bombing outside a Mosul police station, and a US soldier and three policemen were among seven killed in separate explosions and shootings across the country.
Expressing concern, a Vatican spokesman described the attacks as "terrible and worrisome."
Condemning the attack, a spokesman for radical Shiite cleric Muqtada al-Sadr, told Al-Jazeera television that "This is a cowardly act and targets all Iraqis."
"This (attack) isn't against Muslims or Christians, this is against Iraq," Deputy Foreign Minister Labid Abawi was quoted as saying.
According to al-Rubaie, Zarqawi was attempting to create divisions between Muslims and Christians in Iraq, in order to force the Christians to leave the country.