Hezbollah instructors trained Shiite militiamen at remote camps in southern Iraq until three months ago when they slipped across the border to Iran — presumably to continue instruction on Iranian soil, according to two Shiite lawmakers and a top army officer.

The three Iraqis claim the Lebanese Shiites were also involved in planning some of the most brazen attacks against U.S.-led forces, including the January 2007 raid on a provincial government compound in Karbala in which five Americans died.

The allegations, made in separate interviews with The Associated Press, point not only to an Iranian hand in the Iraq war, but also to Hezbollah's willingness to expand beyond its Lebanese base and assume a broader role in the struggle against U.S. influence in the Middle East.

All this suggests that Shiite-dominated Iran is waging a proxy war against the United States to secure a dominant role in majority-Shiite Iraq, which has supplanted Lebanon as Tehran's top priority in the Middle East.

"The stakes are much higher in Iraq, where there is a Shiite majority, oil, the shrine cities and borders with Saudi Arabia," said analyst Farid al-Khazen, a Christian Lebanese lawmaker whose party is allied with Hezbollah.

"The big story is Iraq, and the Americans unwittingly opened it up for the Iranians" by their invasion in 2003, al-Khazen said.

The allegations come as the United States and Iran are engaged in a showdown over Tehran's nuclear program and each country's role in Iraq.

Iran, Hezbollah's mentor, denies giving any support to Shiite extremists in Iraq.

But the three Iraqis who spoke to the AP said the Iranians prefer to use Hezbollah instructors because as Arabs, they can communicate better with the Iraqi Shiites and maintain a lower profile than Farsi-speakers from Iran.

For Hezbollah, a high-risk role in Iraq could give the Lebanese movement leverage with the United States and broaden its appeal within the Arab world where anti-American sentiment remains strong.

Iraqi officials have said little about a Hezbollah role in this country. However, President Jalal Talabani told U.S.-funded Alhurra television this week that "there have been several occasions" when Hezbollah members or those who "claim to belong to Hezbollah" have been detained in Iraq.

He gave no further details.

But the two Iraqi lawmakers and the military officer said Hezbollah instructors work only with members of the Iraqi Shiite "special groups," the U.S. military's name for splinter factions of anti-American cleric Muqtada al-Sadr's Mahdi Army militia. The U.S. believes that Iran's elite Quds Force, a branch of Iran's Revolutionary Guard, supports the special groups.

All three Iraqis spoke on condition of anonymity because they were not supposed to release the information.

The lawmakers belong to al-Sadr's movement and were involved in the creation of the Mahdi Army in 2003. The military officer's job gives him access to highly classified intelligence information.

They said Hezbollah began training Shiite militiamen in the second half of 2006 at two camps — Deir and Kutaiban — east of Basra near the Iranian border. They fled across the border in late March or early April this year after U.S.-backed Iraqi forces launched a crackdown against militias in Basra, Iraq's second-largest city.

In Iran, training resumed in camps once used by Iraqi exiles who fought with Iranian forces during the 1980s war between the two countries, the lawmakers said. Instruction includes explosives, ambushes and use of rockets and mortars.

Citing testimony from special groups members in custody, the officer said the Hezbollah instructors never numbered more than 10 at any one time, kept a low profile and moved back and forth over the Iranian border.

Indications that Hezbollah was playing a role in Iraq first surfaced last July when the U.S. military announced the arrest of Ali Musa Daqduq, a Lebanese-born Hezbollah operative allegedly training Iraqi Shiite militiamen.

At least one other Hezbollah operative, identified only as Faris, was detained in Basra during fighting there in April and was handed over to the Americans, the Iraqi military officer said.

The U.S. military has said little publicly about Hezbollah's involvement here since announcing Daqduq's arrest, though it has frequently alleged an Iranian role in arming, equipping and training Shiite extremists.

"At this point in time, we do not have any new, releasable information regarding Hezbollah's involvement with special groups in Iran and Iraq," a military spokesman, Capt. Charles Calio, said in an e-mail to the AP.

A Hezbollah spokesman in Beirut, Lebanon, refused to comment on any role for his organization.

However, Ibrahim al-Ameen, a Lebanese newspaper editor close to Hezbollah, said in a recent interview in Beirut that Hezbollah's leader, Sheik Hassan Nasrallah, spends several hours daily dealing with "the situation in Iraq."

Nasrallah, who studied Shiite theology in Iraq, spoke at length about Iraqi "resistance" during a speech last May that analysts believed was aimed at bolstering his image as a godfather of Arab opposition to the United States and Israel throughout the Middle East.

Beside its alleged role in Iraq, Hezbollah is known to have ties to the Palestinian militant Hamas group. The charismatic Nasrallah has become a sort of folk hero in the mostly Sunni Arab world after his guerrillas fought Israeli forces to a standstill in a 34-day war in 2006.

A senior Western diplomat based in the Middle East said his government has information suggesting a growing Hezbollah interest in events in Iraq. However, the diplomat would say no more and insisted on anonymity because the subject is so sensitive.

Hezbollah's possible role in direct attacks against U.S.-led forces is murkier and more explosive.

The two Iraqi lawmakers said Hezbollah operatives planned and supervised both the Karbala attack and the brazen daylight kidnapping of five British nationals from a Finance Ministry compound in Baghdad in May 2007. The Britons are still being held.

In the Karbala attack, English-speaking militants wearing American uniforms and carrying American weapons stormed the compound, killing one U.S. soldier and abducting four. The four were later found dead.

A senior Mahdi Army commander in Baghdad, speaking on condition of anonymity because of the sensitivity of the information, said Hezbollah's operations in Iraq had been supervised by Imad Mughniyeh, a top commander of the guerrilla group killed in a car bomb in Syria last February.

The shadowy figure was suspected of a role in the 1983 bombing of the U.S. Marine barracks in Beirut and the 1992 attack on the Israeli Embassy in Buenos Aires, Argentina.