Car bomb attacks against four Shia mosques in Baghdad and one in Kirkuk killed at least 24 people and wounded more than 100, security officials said on Friday.
At least 19 people were killed in the Baghdad attacks, while at least five died in Kirkuk.
A police officer said the deadliest bombing was in western Jihad neighbourhood of Baghdad when a parked car bomb exploded as worshippers were leaving a mosque after Friday prayers. Seven people died there and 25 were wounded.
Another police officer said four worshippers were killed and nearly 20 were wounded in a bombing in eastern Qahira neighbourhood of the Iraqi capital. He said three people died and 15 were wounded in the eastern Zafaraniyah district and that another car bomb killed five and wounded 14 in the northeastern Binook neighbourhood.
Three health officials confirmed the causality figures. All officials spoke on condition of anonymity because they are not allowed to talk to the media.
The bombing in Kirkuk occurred as worshippers were offering Friday prayers in a city mosque, some 250 north of Baghdad, officials said. A further 60 people were injured.