Attacks including bombings against four Sunni mosques killed 28 people in Iraq on Tuesday, officials said, bringing July's death toll to 638, the highest monthly figure in a year marked by spiralling violence.

Another 1,445 people were wounded through July 23, according to AFP figures based on reports from security and medical sources.

The second-deadliest month of the year so far was May, when 614 people died in attacks and 1,550 were wounded. More than 2,900 people have been killed so far in 2013.

A series of bombings targeted worshippers gathered for evening prayers at four Sunni mosques on Tuesday night, killing at least 12 people and wounding at least 49.

A bomb exploded in the Omar bin Abdulaziz Mosque in the northern city of Kirkuk, while another blast struck near Al-Salihin Mosque close by.

And two bombs exploded near Ahmed al-Mukhtar Mosque in the Dura area of south Baghdad, while a car bomb exploded near Al-Imam Ali Mosque in Kut.

Special extended evening prayers are held during the holy Muslim fasting month of Ramadan, which began two weeks ago.

Both Sunni and Shiite places of worship have been attacked in recent months, raising fears of a return to the all-out sectarian conflict that killed tens of thousands of people in past years.

Other violence in the Nineveh and Kirkuk provinces in north Iraq and Diyala and Salaheddin provinces to the north of Baghdad killed 16 people, among them seven police, and wounded eight.

The violence came as Al-Qaeda front group the Islamic State of Iraq and the Levant claimed brazen assaults on two prisons in Iraq that killed more than 40 people and saw hundreds of inmates, including senior militants, escape.

Iraq has faced years of attacks by militants, but analysts say widespread discontent among members of its Sunni Arab minority that the government has failed to address has fuelled the surge in unrest this year.

Sunni Arabs accuse the Shiite-led government of marginalising and targeting their community, including through unwarranted arrests and terrorism charges.

Protests broke out in Sunni-majority areas at the end of 2012 and are still ongoing.

On April 23, security forces moved against protesters near the northern town of Hawijah, sparking clashes that killed 53 people and sending tensions soaring.

More than 450 people have been killed each month since.

In addition to the major problems with security, the government in Baghdad is also failing to provide adequate basic services such as electricity and clean water, and corruption is widespread.

Political squabbling has paralysed the government, which has passed almost no major legislation in years.