A roadside bomb killed four people, including three army soldiers, and wounded 11 people south of Baghdad on Saturday, Iraqi officials said.
The blast took place near the municipal offices of the Rashid district just south of the Iraqi capital as soldiers were responding to an earlier explosion in the same area.
The first explosion, also caused by a roadside bomb, did not cause any casualties.
Police and hospital officials said the three soldiers and a bystander succumbed to their wounds in a Baghdad hospital. They spoke on condition of anonymity because they were not authorized to speak to the media.
Meanwhile, a police spokesman in Diyala province said the head of a five-member family killed on Friday when a roadside bomb hit the car in which they were traveling was a local leader of a government-backed Sunni armed group known as an Awakening Council.
The group's fighters rose up against al-Qaida militants in late 2006 and 2007, first joining the US military in its fight against the terror network and later working with the Shiite-led Iraqi government.
The police spokesman, Maj Ghalib al-Karkhi, had earlier said that the family was not the intended target of the bombing, which struck near the town of Buhriz, 35 miles (60 kilometers) north of Baghdad. The man, his wife and three children - two boys and a 4-year-old girl - were killed in the attack.
Members and leaders of Awakening Councils have been frequent targets of assassinations and bombings blamed on al-Qaida.
Violence has dramatically dropped in Iraq since 2008, but insurgent attacks remain a daily occurrence at a time when US forces are withdrawing, leaving the country's nascent forces alone in charge of security.