Ukraine's defense ministry says it will begin a three-stage withdrawal of its troops from Iraq next week.

The Interfax news agency reports Saturday that 150 of Ukraine's more than 1600 soldiers will leave Iraq on Tuesday.  A full withdrawal should be complete by October.

Meanwhile, Bulgaria says U.S. forces have admitted responsibility for the "friendly-fire" death of a Bulgarian soldier in southern Iraq a week ago.

The Bulgarian defense ministry said the U.S. military said the shooting was "unintentional," but that U.S. troops failed to carefully identify the target and opened fire without warning shots.  There was no immediate confirmation from the U.S. military.

In a separate incident, the U.S. military says it is investigating whether six American soldiers mistreated two Iraqi detainees they were transporting to a detention facility last month. Both detainees sustained minor injuries.