The U.S. military is again accusing Iran of having a hand in attacks on its soldiers in Iraq, alleging it is using Lebanese militant group Hezbollah to arm and train Shia insurgents.

A U.S. general also charged on Monday that Tehran's elite Quds force helped militants carry out a January attack in Karbala in which five Americans were killed.

The information came from the capture of a senior Lebanese Hezbollah operative, Ali Mussa Dakdouk, 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 Shia group led by Qais al-Kazaali, a former spokesman for cleric Muqtada al-Sadr.

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. 

Iran has always denied any involvement in insurgent attacks on U.S. and British forces in Iraq.

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.

Insurgents posed as security team

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 defences 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. 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. Militants abducted four others who were later found shot to death.

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 Shia Muslim militant groups operating in Iraq, but he provided no proof.

With files from the Associated Press