BAGHDAD (AP) – A roadside bomb killed three Iraqi soldiers responding to an earlier blast Saturday in an area south of Baghdad, officials said. One bystander was also killed.

The first explosion near municipal offices in the Rashid district did not cause casualties but was followed by a second bomb as security forces moved toward the scene — a common tactic of insurgents targeting police and soldiers.

Attacks against Iraq’s U.S.-trained security forces have helped undermine public confidence and have sown instability at a delicate time. The country’s politicians remain unable to come together to form a government after a March 7 parliamentary election, and Washington is intent on moving ahead with a U.S. troop withdraw that will leave Iraqi forces on their own.

The victims of Saturday’s attack died of their wounds at a Baghdad hospital, police and hospital officials said. Eleven other people were wounded, the officials said, speaking on condition of anonymity because they were not authorized to release information to the news media.

Also Saturday, new information surfaced about a roadside bombing a day earlier that killed five members of a family driving in Diyala province north of the capital.

A police spokesman said the head of the family was a local leader of a government-backed group of Sunni militiamen known as Awakening Councils.

The group’s fighters rose up against al-Qaida militants in late 2006 and 2007, first joining the U.S. 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 said earlier that the family was not the intended target.

Members of Awakening Councils have been frequent targets of al-Qaida militants.