Two blasts hit a Baghdad Shia neighborhood 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.
Sunni Islamist insurgents and Al-Qaeda's Iraq wing often target Shias 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 an 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, police and hospital officials said.
"We heard an explosion, we rushed out, I saw children running, some with wounds and crying. We evacuated some of the injured people. Mothers were running to the place to find their children," Abu Ahmed, one witness said.
Police said blast on the Iranian pilgrims came from a bomb that had been attached to their bus. It exploded around 300 meters from a police checkpoint, sending the bus out of control before it flipped over on its side.
Insurgents have carried out at least one major attack a month since the last US troops left in December. Iraqi officials worry Syria's crisis is bolstering Iraqi insurgents as Islamist fighters cross into the neighboring 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 targeting Shia neighborhoods that killed more than 100 people.
Security officials had said they believe insurgents would try to carry out a large attack during the religious holiday, which started on Friday.
Car bombs exploded and mortars landed around the Shia neighborhood of Shula, northwestern Baghdad, on Tuesday killing 8 people and wounded 28, and another person was killed by a mortar round in the Kadhimiya area.
