Iraqi security officials say a series of car bombings struck mostly Shi'ite areas of Baghdad on Wednesday, while a mortar attack targeted a Sunni neighborhood.
The car bombings killed at least eight people and wounded 20 others in three areas of the capital, while the mortar attack killed four people in the Azamiyah district.
In Muqdadiyah, to the northeast, a suicide bomber blew up his oil truck at a checkpoint near an Iraqi army base, killing himself and wounding six soldiers.
The U.S. military says one American Marine and three soldiers are the latest U.S. deaths in Iraq from combat.
Tuesday, insurgents carried out several attacks in Iraq, killing more than 50 people, many of them Shi'ite Muslims as they performed rituals for the Shi'ite holy day of Ashura.
During a visit to Turkey today, Syria's foreign minister stressed the importance of the territorial integrity of Iraq. Walid Mualem told reporters the parties in Iraq should unite to solve the security problem. Mualem was in Turkey for talks with officials there.
The United States has accused Syria and Iran of meddling in Iraq, and promoting violence in the neighboring country.