More than 2,500 Iraqis have died in attacks since April, the UN says – with violence at its highest since 2008.
The spike comes amid heightened Shia-Sunni tensions. Sunnis say they are being marginalised by Prime Minister Nouri Maliki’s Shia-led government.
The interior minister said in a statement that the scale of the attacks suggested that militant groups had infiltrated the “social fabric of Iraq”.
The statement added that it would not be possible for security forces to stop the violence without active co-operation from citizens.
The Baghdad bombs, hidden in parked cars, hit markets and car parks in several areas of the city, police say.
The deadliest was said to have hit the eastern Shia district of Sadr City, report say.
A man says he saw vehicles arriving to park shortly before a blast happened in the district of Habibiya, in southern Baghdad.
“We were standing here when a a pick-up truck drove in here and parked there. There were two others cars parking there. Minutes later the car went off,” he told the Associated Press news agency.
One bomb also exploded in Mahmudiya to the south of the capital, killing at least two people.
In the city of Kut, south-east of the capital, at least seven people were killed when two car bombs blew up.
There are also reports of a car bomb going off in Basra, the second city.
This could be the bloodiest month in Iraq for years, says BBC Arabic’s Haddad Salih in Baghdad, with the number of attacks escalating since the beginning of the month of Ramadan earlier this month.
Although the violence is less deadly than that seen during the heights of the insurgency in 2006 and 2007, it is the most widespread since the US military withdrawal in 2011. More than 700 people have been killed in July alone.