A bomb exploded in the Omar bin Abdulaziz Mosqe in the northern city of Kiruk, while another blast struck near Al-Salihin Mosque close by, killing a total of seven people and wounding 31.
Two bombs exploded near Ahmed al-Mukhtar Mosque in the Dura area of south Baghdad, killing at least three people and wounding at least nine.
And a car bomb exploded near Al-Imam Ali Mosque in Kut, southeast of Baghdad, killing two people and wounding nine.
Special extended evening prayers are held during the holy Muslim fasting month of Ramadan, which began two weeks ago.
With the latest attacks, more than 630 people have been killed in violence so far this month, making July the deadliest month in a year marked by spiralling violence.