The attack in Diyala came hours after a female suicide bomber launched an attack in front of a hospital near the city of Falluja in Anbar province.
A woman, a doctor and his wife were killed, with another seven people wounded, doctors said.
The western province of Anbar was a focus for Sunni Muslim resistance groups fighting against US-led forces in the wake of the March 2003 invasion.
Also on Sunday, three Iraqi soldiers were killed and four others wounded by a roadside bomb which targeted an army patrol in the northern city of Mosul.
The attack came on the same day that a car bomb against a police patrol in Mosul wounded 11 people, including five civilians, according to police.
Although there has been a reduction in fighting across Iraq in recent months, certain areas of the country still experience regular attacks, with most of them carried out against US and Iraqi security forces.