Top American officials in Iraq have "strongly condemned" Wednesday's car bombings in the mainly Shi'ite southern city of Amarah that killed at least 40 people and wounded about 125 more.
In a joint statement Thursday, Ambassador Ryan Crocker and the commander of U.S. forces in Iraq, General David Petraeus, also promised to work closely with Iraqi authorities to help bring the attackers to justice.
There has been no claim of responsibility for the three car bombings, targeting a garage, a market and a local police station. Many of those killed were bystanders who had gathered at the site of the first blast.
Iraq's southern Shi'ite-majority areas have been largely free from large-scale attacks. But fighting among rival Shi'ite factions in the region has intensified as the British military hands over security responsibilities to Iraqi authorities.
And, in Britain Wednesday, former Archbishop of Canterbury George Carey appealed for the release of five British men held hostage in Iraq since May.
Last week, their captors released a video that showed one of the hostages and demanded the withdrawal of all British forces from Iraq. The kidnappers did not say what the consequences would be if Britain did not comply.
The four British security guards and one computer expert were seized in May from a Finance Ministry building in Baghdad.