Two blasts hit a Baghdad Shi'ite neighbourhood and a bus full of Iranian pilgrims on Saturday, killing at least 13 people on the second day of the Islamic Eid al Adha religious festival, police and hospital sources said.
Sunni Islamist insurgents and al Qaeda's Iraq wing often target Shi'ites in an attempt to stir up the kind of sectarian tensions that dragged the country close to civil war in 2006-2007 though bombings and attacks have eased.
In one attack on Saturday, a roadside bomb planted near a popular open-air market killed seven people, including three children at a playground. Another blast killed six people when it hit a bus carrying Iranian pilgrims to a Baghdad shrine.
"The blast exploded around 300 metres from our checkpoint. The bus went out of control, hit another car, and flipped over on its side," said a police officer at the scene.
Insurgents have carried out at least one major attack a month since the last U.S. troops left in December. Iraqi officials worry Syria's crisis is bolstering Iraqi insurgents as Islamist fighters cross into the neighbouring country.
The monthly death toll from attacks in Iraq doubled in September to 365, the highest number of casualties in two years, including a series of bombings targetting Shi'ite neighbourhoods that killed more than 100 people.