At least 25 people were killed in the latest wave of attacks across Iraq, including a series of bombings targeting shoppers in a Sunni neighbourhood in Baghdad, authorities have said.

Four people were killed in a twin bomb attack on busy commerical streets in the Dora neighbourhood in the capital on Saturday morning, police sources said. They said three more bomb blasts in the same area later at night killed five people and wounded 21.

Outside of Baghdad, police said a suicide bomber killed five soldiers and wounded eight at a checkpoint in Mishada, around 30km north of the capital. Also on Saturday, police said a roadside bomb killed two soldiers on patrol and wounded five people in Tarmiyah, 50km north of Baghdad.

Health officials, who spoke on condition of anonymity to the Associated Press news agency, confirmed the casualty figures.

Al Jazeera's Baghdad bureau reported that explosions also hit the cities of Baquba, Mosul and Tikrit, killing at least nine and wounding 14.

No group has yet claimed responsibility for the blasts, though Shia fighters have retaliated in the past for attacks by Sunni armed groups.

The Sunni-led violence, part of a series of stepped-up attacks since last year, aims at undermining Iraq's Shia-led government ahead of a crucial vote later this month.

Saturday's attacks come as Iraq is heading toward a crucial parliamentary election on April 30, its first since the 2011 US troop pullout.

More than 9,000 candidates will vie for 328 seats in parliament, but there will be no balloting in parts of the Sunni-dominated Anbar province, which is engulfed in clashes between security forces and al-Qaeda-inspired fighters.

Fighters have seized and are continuing to hold parts of the provincial capital, Ramadi, and nearly all of the nearby city of Fallujah.

Last year, Iraq weathered its deadliest bout of violence since it pulled back from the brink of civil war in 2008. United Nations figures show that violence killed 8,868 people in 2012.

Source: Al Jazeera and agencies