In Baghdad, about 20,000 militiamen loyal to anti-U.S. Shiite cleric Muqtada al-Sadr, many in military fatigues, marched through the sprawling Shiite Sadr City district, which saw some of the worst fighting between Shiite militias and U.S. soldiers before a cease-fire was reached in 2008 that helped stem the sectarian bloodshed that was pushing the country to the brink of civil war.
Similar parades took place in the southern cities of Amarah and Basra, both strongholds of al-Sadr supporters.
Grand Ayatollah Ali al-Sistani, the most respected voice for Iraq's Shiite majority, who normally stays above the political fray, on Friday joined calls for al-Maliki to reach out to the Kurdish and Sunni minorities. A day earlier President Barack Obama challenged the prime minister to create a leadership representative of all Iraqis.
Al-Maliki's State of Law bloc won the most seats in the April vote, but his hopes to retain his job have been thrown into doubt, with rivals challenging him from within the broader Shiite alliance.
The U.S., meanwhile, has been drawn back into the conflict. Obama announced Thursday he was deploying up to 300 military advisers to help quell the insurgency. They join some 275 troops in and around Iraq to provide security and support for the U.S. Embassy and other American interests.
Obama has been adamant that U.S. troops would not be returning to combat, but has said he could approve "targeted and precise" strikes requested by Baghdad.
Manned and unmanned U.S. aircraft are now flying over Iraq 24 hours a day on intelligence missions, U.S. officials say.
Iraq enjoyed several years of relative calm before violence spiked a year ago after al-Maliki moved to crush a Sunni protest movement against what the minority sect claimed was discrimination and abuse at the hands of his government and security forces.
Meanwhile, on Saturday four separate explosions killed 10 people, including two policemen, and wounded 22 in Baghdad, according to police and hospital officials. And in an incident harkening back to the peak days of sectarian killings in 2006 and 2007, two bodies, presumably of Sunnis, were found riddled with bullets in Baghdad's Shiite district of Zafaraniyah, police and morgue officials said.
All officials spoke on condition of anonymity because they were not authorized to speak to journalists.
Associated Press writer Qassim Abdul-Zahra contributed to this report.