Destroyed car is seen at the site of the blast after a car bomb exploded in Basra

A car bomb attack in the southern Iraqi city of Basra has killed at least 20 people and wounded about 40 others.

The blast occurred late Monday in a commercial district where restaurants and shops were packed with people.

Earlier, U.S. military officials said six American soldiers were killed in separate bombings outside Baghdad.

Military officials also reported the death last week of Colonel William Wood -- the highest ranking U.S. officer to die in combat in Iraq. He was killed by an improvised explosive device in the Iraqi capital.

Near the western city of Karabilah, U.S. troops launched airstrikes, killing an al-Qaida leader. Witnesses said the attack killed dozens of civilians, but U.S. officials said they had no reports of civilian casualties.

Some information for this report provided by Reuters and AP.