Washington, Jan 1 - A federal judge has dismissed all charges against five guards of the Blackwater Worldwide security firm in connection with a deadly 2007 shooting in Baghdad.

Judge Ricardo Urbina of the US district court in Washington said Thursday government attorneys misused evidence against the five defendants, forcing him to dismiss the entire case.

The charges arose from a September 2007 incident in which Blackwater guards escorting a diplomatic convoy opened fire in Nisoor Square in Baghdad, leaving at least 34 people dead or injured, including women and children.

Prosecutors said they were unprovoked and that none of those killed were armed or posed a threat to the convoy. The five defendants had faced 14 counts of manslaughter, 20 counts of attempted manslaughter and one count of firearms violation by using an assault gun in the course of committing a crime.

Blackwater Worldwide, based in North Carolina, was contracted by the State Department to protect diplomats and other civilians working in Iraq.

The firm has since changed its name to Xe Services.

The Iraqi government early in 2009 refused to renew the operational licence for Blackwater Worldwide. (dpa)