The morning attacks also wounded at least 54 people, the sources said.
One bomber targeted a joint police and army checkpoint in north Baghdad, while two others struck pro-government paramilitaries on a street in Mishahada, north of the capital, and in a restaurant outside the southern city of Nasiriyah.
Mortar fire also struck houses in Abu Ghraib, west of Baghdad, killing two people and wounding at least seven, officials said.
There was no immediate claim of responsibility for the attacks, but the Islamic State jihadist group frequently carries out suicide bombings in Iraq targeting civilians and security forces.
IS overran large areas north and west of Baghdad in 2014, but Iraqi forces have since regained significant ground with the assistance of US-led air strikes and training.
As IS loses territory, it is increasingly turning to bombings in a bid to stay relevant, a US army officer said.
The group is “losing its prominence on the battlefield, and so what we’ve kinda seen recently is a lot more what we call high profile attacks,” Captain Chance McCraw told journalists in Baghdad.
The jihadists are seeking “to still stay relevant in the media, because that’s how they get their message out,” McCraw said.
A suicide bomber blew himself up following a football tournament south of Baghdad last month, killing more than 30 people. More than 45 people died in a suicide truck bombing at a checkpoint earlier in March.