A series of bombs killed at least 16 people across Iraq on Friday as Shi'ite Muslims celebrated a holy festival, police and medical sources said.
Nine bombs were detonated by remote control. The deadliest were two roadside devices that exploded in quick succession in a market in the Shi'ite town of Yousufiya, 20 km (12 miles) south of Baghdad, killing at least seven people.
It was not immediately clear who was behind Friday's attacks, but Sunni Islamist insurgents who view Shi'ites as apostates have been regaining ground in Iraq this year, reversing a drop in the level of violence.
In Baquba, at least four people were killed by six roadside bombs planted near the homes of Shi'ite families who had recently returned after being displaced from the area due to fear of attacks by al Qaeda Sunni militants.
A roadside bomb exploded in a Shi'ite neighbourhood of western Baghdad, killing at least four people. In Buhriz, a bomb attached to a car killed one member of a Shi'ite family, police said.
Al-Gadeer is one of the biggest festivals for Shi'ites who renew their pledge of allegiance to Imam Ali, the second-most important Islamic figure for Shi'ites after the Prophet Mohammed.
Al Qaeda's Iraqi affiliate was forced underground in 2007 but has now reemerged and earlier this year merged with its Syrian counterpart to form the Islamic State of Iraq and the Levant, which has claimed responsibility for attacks on both sides of the border.
The insurgents have exploited worsening relations between Iraq's Shi'ite-led government and the country's Sunni minority, which complains it has been marginalised since the U.S.-led invasion that toppled dictator Saddam Hussein in 2003.
Violence which had eased after a climax in 2006-07 is now growing again, with more than 7,000 civilians killed this year, according to monitoring group Iraq Body Count.
Last week, a suicide bomber driving a minibus blew himself up outside a cafe in a mainly Shi'ite Muslim district of Baghdad, killing at least 38 people.