Prime Minister Nouri al-Maliki vowed on Thursday to enforce a crackdown on Shiite gunmen despite protests and mounting casualties, as Iraqi troops battled militias in the cities of Basra and Kut.
At least 105 people have died countrywide in clashes since Maliki ordered his troops to crack down on "lawless gangs" in Basra on Tuesday, according to official reports. Some sources have put the toll at double that.
The military operations have been mostly in areas controlled by the Mahdi Army fighters of Shiite cleric Moqtada al-Sadr, severely straining a "freeze" he ordered of the militia's activities last August.
Sadr has threatened to launch a civil revolt if the attacks against his militiamen continue.
Maliki vowed not to back away from the military onslaught.
"We have come to Basra at the invitation of the civilians to do our national duty and protect them from the gangs who have terrified them and stolen the national wealth," he said in a statement.
"We promise to face the criminals and gunmen and we will never back off from our promise," he added.
In Washington, U.S. President George W. Bush called the fighting in Basra a "positive moment" for the development of Iraqi security forces and proof the Baghdad government could defend itself.
In Baghdad, Sadr's followers poured on to the streets to stage noisy protests against the crackdown in Basra and demand the resignation of Maliki, who is personally overseeing the military operations.
In Sadr City, an impoverished Shiite district of around two million people in east Baghdad, crowds gathered in the morning outside the Sadr office to yell slogans against the prime minister.
"Maliki you are a coward! Maliki is an American agent! Leave the government, Maliki! How can you strike Basra?" the crowd chanted.
In the Kadhimiyah neighbourhood of north Baghdad, followers of Sadr carried a coffin covered in red fabric with an attached photograph of Maliki set against the background of an American flag, referring to him as a "dictator."
On Wednesday, Maliki gave gunmen 72 hours to lay down their arms and warned that those failing to do so would face the full brunt of the law.
First signs of a stand-off came in April last year when Sadr withdrew his six ministers from Maliki's cabinet, citing "differences over issues of basic services."
The exit of the ministers was a grave setback for Maliki, whose candidacy for the top job had been supported by Sadr in early 2006 when a wave of sectarian bloodletting was unleashed across Iraq.
Maliki suffered a second setback last September when Sadr's parliamentary bloc pulled out of the Shiite alliance which leads the national unity government in Baghdad.
The Shiite United Iraqi Alliance now consists of just two major parties -- Maliki's Dawa and the Supreme Iraqi Islamic Council (SIIC) of powerful politician and Sadr rival, Abdel Aziz al-Hakim.
Basra has become the theatre of a bitter turf war between the Mahdi Army and two rival Shiite factions -- SIIC and the smaller Fadhila party.
Sadrists accuse the government of favouring SIIC and its Badr Organization militia -- many of them policemen -- at the expense of Sadr's followers.