At least 35 people were killed in a wave of car bomb and mortar attacks in mainly Shi'ite Muslim districts of Baghdad on Tuesday, Iraqi police and medical sources said.
It was one of the most violent days the capital has witnessed since U.S.-led forces began bombing Islamic State insurgents in Iraq last month.
There was no immediate claim of responsibility for the attacks but Islamic State, ultra-radical Sunni Muslim militants who seized swathes of northern Iraq in June, claimed several suicide bombings in the capital earlier this year.
Two car bombs exploded in busy streets in the al-Horreyya district, killing 20 people and wounding 35, according to the police and medical sources. There was also a mortar attack in the Sab al-Bour neighbourhood of northern Baghdad that killed five people and wounded 15.
Later on Tuesday, at least seven people were killed and 18 wounded when a car bomb exploded in the mainly Shi'ite Zaa'faraniya district of southeast Baghdad, police said.
Three mortars also landed in the Shi'ite al-Shula district in the capital's northwest, killing three people and wounding 12, police said.
Baghdad has witnessed relatively few attacks compared to the violence in other areas hit by Islamic State's offensive though bombs still struck the capital on a fairly regular basis. Mortar rounds have a short range compared to rockets, indicating the assailants fired from near the districts.
Security sources say Islamic fighters have tried to use farmland northwest of Baghdad to approach Shi'ite districts.
There were also several small-scale attacks in predominantly Shi'ite areas across the country. In the southern oil hub of Basra, a parked car bomb exploded in a parking lot, setting ablaze five cars but causing no casualties, police said.
In the town of Kifil, near the Shi'ite holy city of Najaf, at least one person was killed and three wounded by a car bomb. And in Kerbala, a car bomb blast on a busy street wounded at least seven people and torched a police car, police said.
In the Kurdish-controlled town of Khanaqin, 140 km (100 miles) northeast of Baghdad, at least four Kurdish security members were killed and 12 wounded in a bomb attack on their patrol, police and medics said.
U.S.-led forces started bombing Islamic State targets in Iraq in August and Washington expanded the campaign to Syria last week in an effort to defeat the well-armed insurgents who have swept through Sunni areas of both Iraq and Syria.
Washington hopes the air strikes, conducted with help from European allies in Iraq and Arab air forces in Syria, will allow government and Kurdish forces in Iraq, and moderate Sunnis in Syria, to recapture territory.