The violence raises the spectre of tit-for-tat killings common during the height of sectarian bloodletting in Iraq that killed tens of thousands of people, and comes at a time of simmering tension between the country's Sunni minority and Shiite majority.
One bomb exploded as worshippers were leaving Saria mosque in the city of Baquba, north of Baghdad, while a second detonated after people gathered at the scene of the first blast, killing a total of 41 people and wounding 57, police and a doctor said.
Security forces cordoned off the area and the main hospital in Baquba, an AFP journalist said.
A string of ambulances carried victims to the hospital, and police and soldiers also helped transport the wounded and dead.
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In Madain, south of Baghdad, a roadside bomb exploded near a funeral procession for a Sunni man, killing eight people and wounding at least 25 others, security and medical officials said.
And a bomb in a coffee shop in the Sunni city of Fallujah, west of Baghdad, killed two people and wounded eight, police and a doctor.