Thousands of demonstrators have demanded the release of Iraqi journalist Muntazar al-Zaidi, who threw both his shoes at United States President George Bush during a news conference on Sunday.
In the mainly Shia Sadr City district of Baghdad, protesters described Mr al-Zaidi as a hero.
The channel he works for, independent Iraqi television station Al-Baghdadia, said he had been exercising freedom of expression - something the US had promised Iraqis on the ousting of Saddam Hussein.
Iraqi officials are facing mounting calls to release Mr al-Zaidi, who was detained after the incident, in which he shouted "It is the farewell kiss, you dog" and threw two shoes at Mr Bush.
Mr Bush ducked, and the shoes missed him. The journalist was immediately wrestled to the ground by security guards and frog-marched from the room.
Soles of shoes are considered the ultimate insult in Arab culture. After Saddam's statue was toppled in Baghdad in April 2003, many onlookers beat the statue's face with their soles.
The Iraqi government branded his actions as shameful and demanded an apology from his Cairo-based employer, which in turn was calling for his immediate release from custody.
Colleagues said he "detested America" and had been plotting such an attack for months against the man who ordered the invasion of his country.
It is not known where Mr Zaidi is being held. Crowds gathered in Sadr City calling for his release.
The BBC reports that the protesters are supporters of Shi'ite cleric Moqtada Sadr, a leading critic of the US presence in Iraq. It said smaller protests were reported in Basra and Najaf.
Saddam's former lawyer, Khalil al-Dulaimi, said he was forming a team to defend Mr Zaidi and that about 200 lawyers, including Americans, had offered their services for free.
Hundreds of Iraqis joined anti-US demonstrations to protest at Mr Bush's farewell visit on Sunday to Iraq, which was plunged into a deadly insurgency and near civil war in the aftermath of the 2003 invasion.