The demonstrations held on Thursday also marked the fall of Saddam Hussein's Ba'ath regime.
The protesters, including Iraqi officials and lawmakers, demanded immediate withdrawal of 'the occupier forces' from the oil-rich country and the release of innocent Iraqis held by US forces.
The demonstrators were chanting slogans saying "NO, No, America" and "No, No, Israel."
The nearly 1.2-million-strong rally also called on the "the government to open investigation about all the crimes that were committed by US soldiers in Iraq since the 2003 US-led invasion," Press TV's Wisam al-Bayati reported.
They also warned against the restoration of the former Ba'athist officials whom they see as 'people with Iraqi blood on their hand'.
The anti-occupation march held just hours after US President Barack Obama paid a surprised visit to the war-torn country on his first trip to Baghdad as commander-in-chief of US forces. Obama has ordered to withdraw all US troops by 2011.
Sadr bloc in the Iraqi parliament has accused the foreign occupiers of inciting violence and orchestrating the recent bomb attacks across the country. The group says the foreign occupiers seek to dominate all internal affairs of Iraq.