Attacks including five suicide bombings hit various areas of Iraq on Monday, killing at least 26 people as parliamentary elections loom next week, the first since American troops departed.

Iraq is suffering a protracted surge in bloodshed that has killed more than 2,750 people so far this year, and the UN envoy warned Monday that militants were seeking to stoke sectarian tensions between the Shiite Muslim majority and the Sunni Arab minority.

In the deadliest attack, a suicide bomber detonated a vehicle rigged with explosives at a police checkpoint in the Suweirah area, south of Baghdad, killing 13 people and wounding 35, a police officer and a medical source said.

Another suicide bomber blew up a vehicle at a checkpoint in Madain, killing at least two people and wounding five, while gunmen shot dead one person and wounded at least one other in Latifiyah, officials said.

In the Sadr City area of north Baghdad, a car bomb in an area of shops killed five people and wounded at least 12. A car bomb in the Shaab area killed at least two people and wounded at least nine.

A suicide bomber also struck a commercial street in the central Karrada district, killing three people and wounding at least 14, while two more suicide bombings in cities north of Baghdad left one person wounded.

Iraqi soldiers and police deployed in force on the street in Karrada that was hit by the blast, which shattered nearby shop windows.

At the site of the explosion, security forces examined a charred piece of what appeared to be human remains, as shop workers and other bystanders looked on.

The attacks came a day after violence in Iraq, including a suicide bombing at Baghdad's Imam Kadhim University, killed at least 16 people.

UN envoy Nickolay Mladenov condemned the attack on the university, which is run by the Shiite religious endowment, as an attempt to stoke sectarianism.

"This is yet another example of sectarian-based violence that the people of this country need to fight in order to bring this country to tranquility, and it is happening at a time when the Iraqi people are preparing to go to the polls in a few days," Mladenov said.

"The target has been selected to incite sectarian hatred."

The April 30 vote is Iraq's first parliamentary election since US forces withdrew in 2011 and is a major test for the security forces.

While they were able to keep violence to a minimum during provincial elections last year, the security forces have failed to halt a surge of unrest this year.

Violence has killed more than 500 people in Iraq so far this month, according to AFP figures based on security and medical sources.

It has been fuelled by widespread anger among the Sunni Arab minority, who say they are mistreated by the Shiite-led government and security forces.

Militant groups have also been bolstered by the civil war in neighbouring Syria.