Intense fighting erupted early today as massive explosions and machine-gun fire ricocheted through the city.
The clashes reportedly broke out as two U.S. helicopters surveyed the battle scene over the city's vast cemetery, a stronghold of al-Sadr's Imam Al-Mahdi Army.
However, U.S. Brigadier General Erv Lessel said today's assault on the center of Al-Najaf excludes a key shrine holy to Shi'ite Muslims, the Imam Ali Mosque.
A high-ranking city official, Jawdat Kadhim, resigned today to protest the U.S. military assault in Al-Najaf, home to around 600,000 people and a traditional seat of Shi'ite learning.
Meanwhile, thousands of Shi'a reportedly took to the streets in a Baghdad district and in the southern city of Al-Basrah to protest against the offensive.
Loyalists to al-Sadr threatened to blow up oil pipelines and port infrastructure in Al-Basrah, pushing oil officials to keep a main southern oil-export pipeline shut. The decision has cut by half Iraq's oil exports to 960,000 barrels per day.
In the southeastern city of Al-Kut, Iraqi officials said at least 72 people were killed and 148 wounded today in U.S. air raids and fighting between the Iraqi police and fighters loyal to al-Sadr.
For more on the situation in Iraq, go to RFE/RL's special page, "The New Iraq."