Security forces used live fire, rubber bullets and shot tear gas canisters in a bid to disperse hundreds of protesters gathered near Tahrir Square.
At least four protesters were killed by teargas canisters in Baghdad on Thursday, medical sources told AFP, the latest deaths from what human rights groups have slammed as a "gruesome" misuse of the weapon
The United Nations had already documented 16 deaths from such military-grade canisters, which are up to 10 times heavier than regular tear gas grenades and can pierce skulls or lungs.
Security forces used live fire, rubber bullets and shot tear gas canisters in a bid to disperse hundreds of protesters gathered near Tahrir Square, a Reuters cameraman said.
Most of those hurt had choked on tear gas or had been hit by rubber bullets and were taken to hospital, medical sources said.
Protesters said the security forces had stepped up their firing of tear gas canisters and rubber bullets early on Thursday morning.
More than 300 people have been killed since October 1, as security forces have fired tear gas canisters and rubber bullets at crowds of protesters.
Prime Minister Adel Abdul Mahdi's government has taken some measures to try to quell the unrest, including handouts to the poor and creating more job opportunities for college graduates.
But it has failed to keep up with the growing demands of demonstrators who are now calling for an overhaul of Iraq's sectarian political system and the departure of its entire ruling elite.
The unrest is among the biggest and most complex challenges to the current ruling elite since it took power after the US invasion and the toppling of Saddam Hussein in 2003.