BAGHDAD, Iraq - As Iraqis awaited the inauguration of their new national unity government, roadside bombs and other attacks killed five Iraqis and wounded 18 people on Friday, including a U.S. soldier riding through Baghdad in a minesweeper.

On Saturday, legislators plan to swear in a new prime minister and Cabinet, completing a democratic transition that began in December with the election of its parliament.

A main goal of the new government will be to restore security in Iraq, where sectarian violence and attacks by insurgents and militias have killed many people and led thousands of Iraqi families to flee their homes.

The Bush administration hopes that full-scale democracy can unite Iraq's complex mix of Shiites, Sunni Arabs and Kurds, reduce public support for insurgent groups and militias, and make it possible to begin withdrawing U.S. troops sometime this year.

In a speech in Baghdad on Thursday night, U.S. Ambassador Zalmay Khalilzad praised Iraq's outgoing prime minister, Ibrahim al-Jaafari, and said the inauguration will be a "historic step in Iraq's transition from dictatorship to democracy."

Since the Iraq war began in March 2003, roadside bombs have been the deadliest form of attack by insurgents, killing thousands of U.S. and Iraqi soldiers and Iraqi police, often by hitting their convoys and patrols in cities such as Baghdad.

On Friday, the day of worship in mostly Muslim Iraq, one such hidden bomb hit a U.S. convoy in Dora, a mixed Sunni-Shiite-Christian area and one of the city's most violent districts.

The blast heavily damaged the armored vehicle used by explosive ordnance disposal teams to search for mines, which often are buried in the dirt beside roads or in piles of garbage. One U.S. soldier was wounded and evacuated from the site in south Baghdad, the U.S. command said.

Two other roadside bombs targeted Iraqi forces in the capital.

One exploded outside the home of a police officer in east Baghdad, said police Lt. Ali Abbas. The officer was on patrol, but the explosion severely wounded his wife and two children, Abbas said.

Insurgents often conduct such attacks in an effort to discourage Iraqis from joining police forces or the Iraq army.

Another roadside bomb exploded near an Iraqi army patrol in western Baghdad, wounding three soldiers, said police Lt. Maitham Abdul-Razzaq.

Police also found the bullet-ridden bodies of four Iraqis who had been kidnapped and tortured by some of the many death squads that are active in the capital. One of the victims was an elementary school teacher. Two of the four bodies were found in Dora. Another beheaded, handcuffed body was found in Numaniya, 80 miles southwest of Baghdad, said Hadi al-Itabi, an official at a morgue in nearby Kut.