The Shias, the country's majority population, punched their fists in the air and chanted "Down, Down USA" outside the presidential palace, home to the US occupation administrator Paul Bremer.
The protesters, about 3,000, yelled "We are soldiers of Sadr," a reference to the prominent Shia cleric Moqtada Sadr who fired off a vitriolic denunciation on Friday of the US-led occupation and the new transitory 25-member Governing Council under its wing.
The protests started after reports that US soldiers and armoured vehicles surrounded the cleric's home on Saturday for several hours in the Shia holy city of Najaf, 180 km south of Baghdad, as helicopters hovered overhead. Sadr’s supporters in Najaf too staged demonstrations.
Further south, in the Shia heartland, demonstrations also flared in the port of Basra, with protesters hurling stones.
Sadr has also announced the formation of an armed group “Mehdi Army”. On Saturday, recruitments for the group commenced in the Baghdad suburb of Sadr city.
Earlier in the day, a US soldier was gunned down in Baghdad by resistance fighters. He was the 35th US soldier killed in action since major combat was declared over on May 1.
New Iraqi army
Meanwhile, recruitment began on Saturday for a downsized Iraqi army that will replace the military of the previous Saddam Hussein government, the US military said.
Occupation forces to form
new Iraqi army
Several hundred Iraqi men, many of them soldiers of the previous army, filled out application forms in Baghdad hoping to join the first 1,000-strong light-armoured mechanized infantry battalion. The US occupation forces said training of the new battalion would commence in August.
Besides Baghdad, recruitment had begun in the southern city of Basra and Mosul in the north, a statement in Baghdad signed by Brigadier Jonathon Riley said.
Recruits will be paid $ 60 per month, Riley said. The new army aims to have a nucleus of 12,000 men within a year and a full 40,000 in two years' time.
Iraq's US occupation administrator Paul Bremer abolished the Saddam Hussein government’s 400,000-strong military in May.