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Iran is using the Lebanese Shiite militia Hezbollah as a "proxy" to arm Shiite militants in Iraq and Tehran's elite Quds force helped militants carry out a January attack in Karbala in which five Americans were killed, a U.S. general said Monday.

A senior Lebanese Hezbollah operative, Ali Mussa Dakdouk, was captured March 20 in southern Iraq, U.S. military spokesman Brig. Gen. Kevin J. Bergner said. Dakdouk served for 24 years in Hezbollah and was "working in Iraq as a surrogate for the Iranian Quds Force," Bergner said.

The general also said that Dakdouk was a liaison between the Iranians and a breakaway Shiite group led by Qais al-Kazaali, a former spokesman for cleric Muqtada al-Sadr. Bergner said al-Kazaali's group carried out the January attack against a provincial government building in Karbala and that the Iranians assisted in preparations. Al-Khazaali and his brother Ali al-Khazaali were captured with Dakdouk.

Dakdouk told U.S. interrogators that the Karbala attackers "could not have conducted this complex operation without the support and direction of the Quds force," Bergner said.

Documents captured with al-Khazaali showed that the Quds Force had developed detailed information on the U.S. position at the government building, "regarding our soldiers' activities, shift changes and defenses, and this information was shared with the attackers," Bergner said.

The Karbala attack was one of the boldest and most sophisticated against U.S. forces in four years of fighting in Iraq, and U.S. officials at the time suggested Iran may have had a role in it. In the assault, up to a dozen gunmen posed as an American security team, with U.S. military combat fatigues, allowing them to pass checkpoints into the government compound, where they launched the attack. One U.S. soldier was killed in the initial assault, and the militants abducted four others who were later found shot to death.

The U.S. military in the past has accused the Quds Force — the external arm of Iran's elite Revolutionary Guards — of arming and financing Iraqi extremists to carry out attacks on U.S. and Iraqi forces. Tehran has denied the U.S. accusations.

Hezbollah spokesmen in Lebanon said they were checking into the claims Dakdouk was a member of the group and would not comment. The group has in the past denied any activities in Iraq. In late 2005, British Prime Minister Tony Blair said his government suspected that Iran and Lebanon's Hezbollah might be supplying technology and explosives to Shiite Muslim militant groups operating in Iraq, but he provided no proof.

Bergner said Iraqi extremists were taken to Iran in groups of 20 to 60 for training in three camps "not too far from Tehran." When they returned to Iraq, they formed units called "special groups" to carry out attacks, bombings and kidnappings.

"Our intelligence reveals that the senior leadership in Iran is aware of this activity," he said. Asked if Iran's supreme leader Ayatollah Ali Khamenei could be unaware of the activity, Bergner said, "That would be hard to imagine."

Dakdouk was "tasked to organize the special groups in ways that mirrored how Hezbollah was organized in Lebanon," the general said. Dakdouk was ordered by Hezbollah's leadership to work with the Quds Force and went to Iran in May 2006 to meet with Quds Force commanders, Bergner said. He then made four trips to Iraq over the next year.

Hezbollah, he said, helps the Iranians as a "proxy ... to do things they didn't want to have to do themselves in terms of interacting with special groups," Bergner said. He added that Hezbollah did not appear to have an extensive network in Iraq, saying Dakdouk was "being used specifically as a proxy by the Quds Force.

Meanwhile, two U.S. soldiers were killed in shooting attacks on their patrols in Baghdad, where American forces are carrying out an intensified crackdown to uproot insurgents, the military said Monday.

The two deaths took place in separate attacks Sunday, the military said in a statement. In one, a U.S.-Iraqi patrol was hit by a roadside bomb in a western district of the capital, then gunmen opened fire, killing one American soldier and wounding two Iraqi policemen.

The second soldier was killed when gunmen attacked his patrol in southern Baghdad, the military said in a statement. Both soldiers' names were not released pending notification of their families.

The deaths brought to 3,579 the number of members of the U.S. military who have died since the beginning of the Iraq war in March 2003, according to an Associated Press count. The figure includes seven military civilians. At least 2,936 died as a result of hostile action, according to the military's numbers.