At least 10 people have been killed by a parked car bomb in an open-air market north-east of Baghdad, in an attack police said was aimed at them.
More than two dozen others were wounded in the blast at Balad Ruz market, which was packed with shoppers.
The attack was aimed at a passing patrol, police said, but nearly all the victims were civilians.
In the same Diyala province, insurgents opened fire on minibus passengers, killing five people, police said.
Diyala is one of the most violent provinces in Iraq. It is mainly Sunni, but also has significant Shia and Kurdish populations.
Balad Ruz is a Shia enclave, and has been the target before of attacks blamed on al-Qaeda-linked Sunni insurgents.
At least 26 people died there on 7 March when a cafe was blown apart by a bomb.
US commanders have sent thousands of extra troops to Diyala in an attempt to quell the violence there.