It was the latest in a surge in violence that has swept across Iraq since April, reaching levels unseen since the country teetered on the brink of civil war in 2006 and 2007.
A bomb went off at an outdoor market in Baghdad's southeastern suburb of Nahrawan, killing three shoppers and wounding 10, a police officer said.
Another bomb targeted worshippers as they were leaving a Sunni mosque after Friday prayers in the capital's southwestern Saydiyah neighbourhood, killing three and wounding nine, another police officer said.
In Abu Ghraib, just west of Baghdad, one worshipper was killed and six others were wounded when a bomb went off near a Sunni mosque, the police said.
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To the north of the Iraqi capital, a bomb targeted a patrol of pro-government anti-al-Qaeda Sunni militiamen in the town of Tarmiyah, killing three and wounding two, police said.
Al-Qaeda sees the militia, known as Awakening Council, as traitors since it was set up by the US forces during the height of Iraq's insurgency. Tarmiyah is located about 50 kilometres from Baghdad.
Medical officials confirmed the causality figures. All officials spoke on condition of anonymity because they were not authorized to talk to media.
The explosions came a day after a series of attacks killed at least 50 people yesterday. And on Wednesday, coordinated explosions hit mainly Shiite commercial areas in Baghdad and outside the capital, killing at least 35 people.
Bombings and militant attacks have spiked since April, when security forces carried out a bloody raid on a Sunni protest camp in the country's north, pushing violence to the highest levels in years and killing more than 5,500 people, according to the United Nations.