A wave of attacks targeting commercial areas in and outside Baghdad has killed a total of 47 people, officials have said.
They said the deadliest of Monday's bombings was carried out by a suicide bomber who blew up himself among Shia worshippers who were leaving a mosque after noon prayers in the capital's eastern New Baghdad area, killing at least 15 people and wounding 26 others.
Six people were killed and 11 wounded when two car bombs detonated less than two minutes apart hitting a restaurant on a commercial street in northern Baghdad, officials said.
Earlier in the day there were back-to-back car bombings in cities south of Baghdad.
In Karbala, an explosion killed 15 civilians and wounded 31 others. In Babel, two car bombs went off in separate areas, killing 11 people and wounding 29 others.
Al Jazeera's Zeina Khodr, reporting from Erbil, said Monday's bombings targeted mainly Shia areas.
"Babel and Karbala are Shia-populated cities and we understand the caretaker Prime Minister Nouri al-Maliki was in Karbala at the time of the attack.
"In Baghdad a Shia mosque was targeted by a suicide bomber, the second attack of its kind in just four days.
"There is a growing fear that Iraq is descending back into sectarian violence. Four days ago Sunni worshippers came under attack when gunmen opened fire in a mosque."
Since early this year, Iraq has been facing increasing levels of violence from the Islamic State group and other Sunni fighters who have taken over areas in the country's west and north.
The crisis has worsened since June when the Islamic State declared a caliphate in territory under its control.
Crimes against humanity
On Monday, UN human rights chief Navi Pillay condemned "appalling, widespread" crimes being committed by Islamic State forces in Iraq, including mass executions of prisoners and "ethnic and religious cleansing".
"Grave, horrific human rights violations are being committed daily by the Islamic State group and associated armed groups," Pillay said, citing targeted killings, forced conversions, abductions, slavery, sex crimes, forced recruitment and destruction of places of worship.
"They are systematically targeting men, women and children based on their ethnic, religious or sectarian affiliation and are ruthlessly carrying out widespread ethnic and religious cleansing in the areas under their control."
The violence and political divisions have thrown Iraq into deep crisis. At his first press conference since accepting the nomination to be Iraq's next prime minister, Haider al-Abadi on Monday called on the country's numerous militias and tribes to come under government control and stop acting independent of the government.
Abadi said that the phenomena of militias roaming the streets alone "worries me and I consider it very dangerous".
The new prime minister, who has until September 10 to form a new government, said he was optimistic he would make that deadline.