NAJAF, Iraq -- More than 1,000 Shiite Muslim demonstrators clashed last night with supporters of influential Shiite cleric Muqtada Sadr in the southern Iraqi city of Najaf, leaving at least seven people dead and dozens wounded, according to officials at a local hospital.

Waving banners demanding the "expulsion of the outsiders," the crowd gathered near the Shrine of Ali -- a holy site for Shiites -- to call on the provincial governor to banish Sadr's Mahdi Army. Many residents of Najaf blame Sadr for heavy damage the city sustained during a Mahdi Army uprising against U.S. forces a year ago.

The new violence came as the Pentagon announced it was ordering 1,500 paratroopers from the 82nd Airborne Division to Iraq to provide security for the scheduled Oct. 15 referendum on the proposed constitution and the December national elections, The Associated Press reported.

Witnesses attributed yesterday's violence to rifle-toting special forces from Iraq's Shiite-dominated Interior Ministry who had been deployed to the scene. Aides to Sadr said the final death toll could rise substantially.

"This is a savage action done by uncivilized people. They don't have any Iraqi honor," said Nassar Zeghayir Rubaie, a National Assembly member aligned with Sadr.

Iraq's ministers of health and transport and 21 other lawmakers who belong to a political movement inspired by Sadr's late father, a revered Shiite cleric, said they would boycott their positions in protest. Mahdi Army forces were put on "emergency status" across the country, according to Rubaie.

Iraqi security forces imposed an overnight curfew, and U.S. soldiers arrived in Najaf after midnight, blocking all entrances into the city. A civilian driving toward the American troops was shot dead at about 1:30 a.m. today.

In Baghdad, news services reported late yesterday that Sadr's forces attacked three offices of the Badr Organization, a rival Shiite militia that often operates as part of Iraq's security forces, particularly in the south.

The fighting yesterday fueled fears of a violent rift within Iraq's Shiite community, which accounts for the majority of the country's 26 million people and holds the most powerful positions in the transitional government.

Sadr's Mahdi Army, largely composed of Shiites from impoverished sections of Baghdad and several southern cities, has long had tense relations with the Badr militia, which is the armed wing of the powerful Supreme Council for Islamic Revolution in Iraq. But the two groups have not fought openly before.

The clashes came as political factions across the country, including Sadr's supporters, continued to stake out positions on Iraq's constitutional referendum, slated for Oct. 15. The proposed constitution was submitted to the National Assembly on Monday, with some disputed articles left open for discussion, and is expected to be ratified today.

Most Shiites are likely to vote in favor of the constitution, whose drafting was dominated by key figures of the Shiite-led government. Sadr, an outspoken nationalist and critic of the U.S. presence in Iraq, has not yet declared his position on the document. But his supporters have threatened to join Sunni Arabs in voting against it in the referendum if it devolves power from Iraq's central government to autonomous regions.

"We are ready, by a single phone call within a minute, to defeat the constitution by voting against it in six provinces: Diwanya, Samawa, Nasiriya, Amara, Basra and Sadr City in Baghdad," said a Sadr spokesman, Jaleel Musawi.

Highlighting their potential alliance, hundreds of Sunnis and Sadr followers gathered in the northern city of Hawija to call for opposition to the constitution.

"The Sunnis and their supporters among the Shiites will continue to demonstrate to safeguard the unity of Iraq, and reject partition and division," said Rakan Abdulla, a city council member from the nearby city of Kirkuk.

In Baghdad, as politicians gathered in an attempt to resolve remaining disagreements over the constitution, leaders of two of the country's most prominent Sunni organizations, the Muslim Scholars Association and the Sunni Bloc, criticized the constitution-writing process.

"Our conference believes that if this draft is approved by the National Assembly as it is now, it will be illegitimate and doesn't represent all the Iraqi factions," Sunni Bloc leader Adnan Dulaimi said in a news conference.

Hussein Shahristani, a Shiite who is deputy chairman of the National Assembly, said that during yesterday's negotiations Sunnis were hoping to eliminate a section barring former members of Saddam Hussein's Baath Party from some government posts and were seeking to empower the country's parliament to veto attempts by provinces to form regional governments.