At least 16 people were killed by a suicide bomber at what was a crowded cafe in the Iraqi city of Balad.
More than 40 more were wounded in the attack on Monday.
The city's mayor said all the casualties were civilians.
As residents cleared the debris and security forces inspected the scale of the devastation other attacks were taking place elsewhere in Iraq the same day.
Two roadside bombs near a playground and a school in the town of Muqdadiya killed six more people and wounded dozens, some of them children.
In the city of Mosul three soldiers on their way to join their unit were shot dead by gunmen who intercepted their car.
It wasn't immediately clear who was behind the latest wave of bloodshed.
The main suspect is a group calling itself the State of Iraq and the Levant formed this year though a merger of al Qaeda's affiliates in Iraq and Syria.