Supporters of Iraq s Coordination Framework lift national flags and placards during a rally outside the capital Baghdad s high-security Green Zone, on August 12, 2022. AFP
The opposing demonstrations were the latest turn in a standoff which has so far remained peaceful in the war-scarred country.
Thousands of supporters of Sadr, who once led a militia against American and Iraqi government forces, gathered for the Muslim weekly prayers near parliament inside the normally secure Green Zone.
A week earlier, Sadr had called out tens of thousands of his followers for prayers in the area, home to government and diplomatic buildings.
For nearly two weeks, his supporters have since held daily sit-ins, first inside the legislature, and later on its grounds.
Their protest, triggered by a rival bloc's pick for prime minister, reflects months of failed negotiations by Iraq's political forces to form a new government after October elections.
Outside parliament Umm Hussein, a Sadr supporter in her 50s, said she was there to protest "the regime that for 20 years has done nothing for the people, except plunder and steal public money".
"Ninety percent of the population live in poverty, in sickness, in hunger," she complained, demanding "new faces" at the helm who would "serve the people".
On Wednesday, Sadr demanded the judiciary dissolve parliament by the end of next week, as part of his call for new elections.
'Protect the constitution'
His rivals in the pro-Iran Coordination Framework started a counter-demonstration later Friday.
Several thousand protesters waving the national flag gathered on a road leading towards the Green Zone, an AFP correspondent reported.
Loudspeakers played the national anthem.
A statement from the alliance demanded the "formation of a new government" that would provide public services and solutions to power outages and water shortages.
"We're here to protect the state and the constitution," said Abu Mehdi, a protest organiser from the city of Hilla, south of the capital.
"Give the Coordination Framework the chance to form a government."
Sadr's supporters also rallied Friday in the southern cities of Amarah, Kut and Nasiriyah. Their rivals demonstrated in the main northern city of Mosul, AFP correspondents reported.
To further his campaign for new elections, Sadr has called on his supporters to petition the courts en masse.
Stewards handed out printed forms outside parliament on Friday, to which demonstrators only had to add their names and signatures.
The Framework had initially said they were conditionally open to new elections
Asked what he would do if the courts rejected the petitions, 32-year-old engineer Ahmed al-Ibrahimi said: "Revolution is a lengthy struggle. Beating the retreat is not in our vocabulary.
"We will keep up our sit-in and we will maintain our demand for the overthrow of this corrupt political junta."
Two days after Sadr supporters stormed the Green Zone and entered parliament on July 30, thousands of Coordination Framework backers held a counter-protest on a road leading to the Green Zone.
Police fired water cannons to prevent them from entering the area, and they dispersed after about two hours.