STORY: Demonstrators opposed to al-Sadr had staged a protest on Monday (August 1) at the edge of Baghdad's fortified government zone, where Sadr's supporters were holding an open-ended occupation of Iraq's parliament.
The Sadrists have called for new elections and an end to the political system that has existed since the U.S.-led invasion which toppled Sunni dictator Saddam Hussein.
The rival Shi'ite Muslim groups are affiliated with heavily armed militias, raising fears of clashes as tension soars over the failure to form a government nearly 10 months after an October election - the country's longest post-election deadlock.
Sadr's opponents include a grouping of parties and militias mostly aligned with Iran. That grouping, known as the Shi'ite Coordination Framework, said Monday's protest aimed to protect state institutions against the civil unrest of the Sadrists.
Sadr came first in the October election, but withdrew all his lawmakers from parliament after he failed to form a government that excluded his Shi'ite rivals.