Security forces deployed in force on Sunday to block protesters from bridges leading to the highly-fortified Green Zone, which houses some of the main government offices and foreign diplomatic missions, including the US Embassy.
Police used tear gas and water cannons against protesters, who hurled rocks.
According to reports, some demonstrators threw Molotov cocktails, and others set fire to tires during the protest.
At least seven people have been injured by tear gas canisters, police sources said, while a military spokesman said in a separate statement that at least 32 members of the security forces were wounded by hand grenades thrown by a group he suggested had hidden among otherwise peaceful demonstrators, without elaborating.
Similar protests also took place in several southern cities, including Basra, Najaf and Nasiriyah.
Iraqi Shia leader and cleric Moqtada al-Sadr warned on Sunday that foreign-backed rioters were turning the protests into violent confrontations with security forces.
Protests erupted in Iraq in October last year over unemployment and a lack of basic services, with demonstrators calling for economic reforms and a meaningful fight against corruption in state institutions.
Reports say some 550 people were killed and 30,000 injured as the anti-government rallies took a violent turn.
The protests led to the resignation of prime minister Adil Abdul-Mahdi, who was replaced by Mustafa al-Kadhimi in May following months of political deadlock.
In a televised address on Saturday, Kadhimi vowed to hold early and fair elections, a demand of many protesters, and called on security forces not to fire at demonstrators, but also called on protesters to “respect the uniform”.