Brig. Gen. Kevin Bergner told reporters in Baghdad Monday that detainees facing accusations of ordering the Karbala assault have confessed that senior operatives from Iran supported the attack.

According to Bergner, the militants said "senior leadership leading the Quds Force knew of and supported planning for the eventual Karbala attack that killed five coalition soldiers."

Bergner reported the connection was made by a senior Lebanese Hezbollah operative, Ali Mussa Dakdouk, who was captured in southern Iraq on March 20. Bergner claimed Dakdouk served 24 years in Hezbollah and had gone to Iraq "as a surrogate for the Iranian Quds force."

According to Bergner, Dadouk served as a liaison between Iran and Qais al-Kazaali, a former spokesman for cleric Muqtada al-Sadr who now leads his own Shi'ite group. Bergner said al-Kazaali's group carried out the brazen Karbala attack when gunmen, disguised as Americans, tricked their way into a government compound, killing one U.S. soldier immediately and abducting and later killing four others.

Bergner said the attackers spoke English, wore American-looking uniforms and carried U.S.-style weapons, which helped get them through Iraqi checkpoints. Bergner blamed the sophistication of the attack on the Qods Force.

"The Qods Force had developed detailed information regarding our soldiers' activities, shift changes and defences, and this information was shared with the attackers," Bergner said.

Bergner also reported the US had discovered three small camps near Tehran where Qods Force and Hezbollah operatives were training between 20-60 Iraqi Shi'ite militants at any given time.

US commanders have previously accused Iran of financing and arming the Iraqi militants, but this was the first time they have alleged that Iranian officers had prior knowledge of the attack.