Hundreds of people marched in Najaf on Tuesday calling on rebel Shia cleric Moqtada al-Sadr to pull his militia out of the Iraqi holy city.
Witnesses said they marched to the central shrine area of the city before dispersing peacefully.
US forces have surrounded the city as part of a campaign to crush Sadr's fighters and end a month-long uprising that erupted in Baghdad and cities across the Shia south.
Sadr, who is wanted in connection with the murder last year of a rival cleric, is opposed by much of the mainstream Shia religious establishment, which has urged him to end his stand-off with US forces and pull his fighters from mosques.
The commander of US forces in the Middle East has said that although his forces are wary of taking their fight with Sadr to shrines Shias hold sacred, they will not hold off attacking the rebel cleric's forces indefinitely.