The families of three American soldiers killed during a brazen attack in Iraq are suing the Iranian government for allegedly orchestrating the raid.

Filed late Monday in U.S. District Court in Washington, the lawsuit says Lt. Jacob Fritz, Specialist Johnathan Chism, and Private First Class Shawn Falter were taken prisoner and then murdered in January 2007 by Iranian-backed Hezbollah agents and the Khazali network, an Iraqi militant group also funded and trained by Iran.

The lawsuit says Iran directed the assault on the provincial headquarters in Karbala as retaliation for the arrest of Iranian agents operating in Iraq by U.S. forces.

The attack 50 miles south of Baghdad was one of the boldest and most sophisticated during eight years of warfare in Iraq. Gunmen posed as a U.S. security team to get past the headquarters checkpoint manned by Iraqi police. They traveled in black SUVs, had American-style weapons, wore U.S. military combat fatigues, and spoke English.

Once past the checkpoint, several of the gunmen got out of the SUVs and spoke with Falter and Chism, who were on guard, and then headed into the headquarters. They shot the two soldiers as they passed by. Both were taken wounded but alive, the lawsuit said. They resisted capture as best they could despite their injuries.

Fritz and another Army officer were captured in one of the compound's offices after the gunmen fired their weapons and threw a grenade. The family of the other officer is not part of the lawsuit.

The attackers fled with their captives and headed east toward the Iranian border, according to the complaint. They were handcuffed in pairs and shot.