Fighting between Iraqi government forces and militias loyal to Shiite leader Moqtada al-Sadr erupted Tuesday in the southern port city of Basra, as well as other towns and certain districts of Baghdad. Dozens were killed in the conflicts, according to the media and hospital officials.

The new round of fighting threatens to unravel the fragile truce between Sadr’s Mahdi Army militia and the US and its puppet regime in Baghdad, declared by Sadr in August 2007 and reaffirmed in February, a factor in the relative decline of deadly violence in Iraq over the past six months. The Bush administration’s claims of “success” in its military surge are likewise at risk.

One Mahdi Army militiaman, reached by telephone in Baghdad’s Sadr City, told the Christian Science Monitor, “The cease-fire is over; we have been told to fight the Americans.” One official in Sadr’s Basra office, speaking on condition of anonymity, informed a Los Angeles Times reporter, “The Sadr current is threatening to set fire to the oil wells in Basra if the Iraqi military continues its security plan.”

Prime Minister Nouri al-Maliki’s government initiated the latest violence by launching a major military campaign early Tuesday morning against Sadr’s forces in Basra, the center of Iraq’s oil industry. While the US media passes along the claim that the assault came in response to clashes in recent days between Iraqi police and army forces and elements of Sadr’s Mahdi Army, the operation, codenamed Saulat al-Fursan (Charge of the Knights), was obviously planned well in advance, with the support or insistence of the American and British military. The New York Times noted in passing that “senior Iraqi officials had been signaling [the operation] for weeks.” As many as 15,000 Iraqi troops are involved.

The Times reported that over Basra, “What appeared to be American or British jets also soared through the skies, witnesses said, providing air support.” According to DPA, the German news agency, several US military aircraft were spotted landing in that city Tuesday. Reuters noted that a witness reported Tuesday seeing a long column of US armored vehicles entering the Sadr City area of Baghdad.

Maliki arrived in Basra Monday to supervise the military operation, which includes a 10 p.m. to 6 a.m. curfew, the closure of all schools for three days and a ban on all vehicles entering the province until further notice. “The prime minister is keen to be on the ground near the operation, dealing closely with the issue rather than dealing with it through reports,” Sadiq al-Rikabi, the prime minister’s political adviser, told the Times.

While the Iraqi regime asserts that the purpose of the operation in Basra is to wrest control of the city from the various Shiite militias, as well as “criminal gangs” and oil smugglers, news reports make clear that the Mahdi Army is the principal target of the assault. According to CBS News, its chief foreign correspondent Lara Logan reports that the Mahdi Army “was clearly in the crosshairs, feeling the brunt of the attack, and defending themselves fiercely.”

Battles were reportedly fiercest in the poor central and northern districts of Basra, where Sadr has the strongest support.

The French news agency AFP reported that mortar and gunfire could be heard after Iraqi security forces entered the neighborhood of al-Tamiya, a Mahdi Army stronghold. The fighting apparently spread to five other districts, including al-Jumhuriya, Five Miles and al-Hayania. Residents told the Washington Post they saw military vehicles and “soldiers and policemen exchanging fire with armed groups.”

Al Jazeera reports that in retaliation a number of presidential palaces and Iraqi security and military bases in Basra “came under intensive attack during the assault. Mahdi Army forces also stormed the main Iraqi army base in Shatt al-Arab camp in the city.” Sadr supporters, according to one press account, also attacked the offices of Maliki’s Dawa Party, and fought with guards, an episode that resulted in seven deaths. In addition, government sources said that the Mahdi Army attacked a number of security checkpoints. The latter’s spokesmen, in fact, announced it had taken over Iraqi army checkpoints.

The Los Angeles Times commented, “Heavy explosions and machine-gun fire rocked the city [Basra], where rival political factions, their allied militias and criminal gangs are vying for control of oil exports that generate most of Iraq’s government revenue.” Since the British withdrew from the city in December, three rival factions—the Mahdi Army, the Badr Brigade, associated with the pro-Iranian Supreme Islamic Iraqi Council (SIIC), and the Fadila (Virtue) Party, which has a following among the Shiite poor in the south and particular influence in the oil industry—have been battling it out for control.

Iraqi security forces Tuesday told DPA that more than 50 of the injured in Basra, most of them Iraqi troops and police officers, were admitted to al-Sadr hospital. Sixteen bodies were also taken to the facility. Mawani Hospital received 18 wounded and five corpses. Four militants from the Mahdi Army were among the dead.

Gunfights and unrest also broke out in a number of other cities and towns in southern Iraq. In Kut, Mahdi Army forces were reportedly in control of five of the city’s 18 districts. US warplanes were circling overhead. A local police captain told Reuters, “We ask US forces to help us with aircraft and vehicles. The militants have spread throughout Kut.” In Hilla battles between the Mahdi Army and police occurred in two neighborhoods.

In Samawa, capital of southern Muthanna province, police imposed a curfew after Sadr’s forces appeared on the streets. Curfews were also declared in Hilla, Kut, Nassiriya and Diwaniya.

In Baghdad, US and government forces sealed off Sadr City, with its 2 million slum-dwellers, and fighting erupted for the first time since last October between US and Mahdi Army forces. According to the Christian Science Monitor, “Sadr City residents say they saw fighting Tuesday between Mahdi militiamen and US and Iraqi forces in several parts of the district. One eyewitness, in the adjacent neighborhood of Baghdad Jadida, who wished to remain anonymous, said he saw a heavy militia presence on the streets, with two fighters planting roadside bombs on a main thoroughfare.”

A US military spokesman told the media that over the course of 12 hours Tuesday, 16 rockets were fired at the Green Zone and 18 mortar rounds fell on US bases and outposts on the east side of Baghdad. A mortar round hit a US patrol in the Adhamiyah district, killing one soldier. A roadside bomb set an American Humvee on fire, but all the occupants escaped. Several clashes broke out between US forces and militiamen when the latter attacked several government checkpoints.

Sadr supporters also marched in protest Tuesday in Baghdad against the government crackdown in Basra and recent arrests of Mahdi Army personnel, whose number its spokesmen claim runs into the thousands.

In response to the government assault, three of Sadr’s chief aides held a press conference in Najaf and accused Maliki of pursuing a US agenda. They also threatened to continue the campaign of national protest and civil disobedience if US and Iraqi forces continue to attack the Mahdi Army.

In advance of the Basra operation, the Sadrist movement had already designated Monday and Tuesday days of protest, as part of a civil disobedience campaign, calling on shopkeepers in Baghdad to shut down, as part of the campaign to win the release of jailed Mahdi Army personnel and for an end to US-Iraqi raids and other attacks on their movement.

Sadr issued a statement Tuesday calling for sit-ins and threatened “civil revolt.” He declared, through an aide, “We demand that religious and political leaders intervene to stop the attacks on poor people. We call on all Iraqis to launch protests across all the provinces.

“If the government does not respect these demands, the second step will be general civil disobedience in Baghdad and the Iraqi provinces.” Other reports indicate efforts by Sadr’s representatives to bring an end to the fighting in Basra and generally defuse the situation. Sadr has come in for sharp criticism within his own movement for the cease-fire deal he made with the US and the Maliki government.

The Sadrist forces accuse Maliki and the SIIC of organizing recent attacks as part of an effort to retain control in the October provincial elections. Sadr’s movement boycotted the last provincial elections in 2005, giving the Supreme Council and Maliki’s party the lion’s share of political power in southern Iraq.

Behind the conflict in Basra, as one news agency notes, stand “rival political powers and business interests, which dominate the economy, the oil industry and security bodies.” One Arab journalist told DPA, “The militiamen serve the interests of rival politicians and businessmen.”

Along with providing support for the assault on Basra, the US military is attempting to turn the current conflict into another means of ratcheting up the tension with Iran.

After rockets hit the Green Zone Sunday, US commander in Iraq Gen. David Petraeus claimed, without providing any proof, that the weapons had been provided by Iran. On Tuesday, Rear Adm. Greg Smith, spokesman for the US-led forces, blamed the Quds unit of Iran’s Revolutionary Guards for supplying the 107- and 122-millimeter rockets that hit the area.

Smith declared, “We believe the violence is being instigated by members of special groups that are beholden to the Iranian Quds Force and not Sadr.... Although we are concerned, we know that very few Iraqis want a return to the violence they experienced before the surge.”

The Christian Science Monitor observed, “There is growing concern, however, that Iran could respond to such US accusations.” The newspaper cites the comments of Martin Navias, an analyst at Britain’s Centre for Defence Studies at King’s College in London: “This is pretty serious, and if the Iranians do not back down rapidly this will escalate. The US has a number of problems with Iran, mainly the nuclear program and its behavior in Iraq. There are many people in the Bush administration who want to hit Iran.”

In another provocation, during the assault on Basra Tuesday, a contingent of occupation forces, including US and British troops, mobilized at the nearby border with Iran and sealed it off.

In fact, according to the German news agency DPA, the Iranian regime “wants to liquidate” the Sadr movement “and is pressing its allies within the Iraqi government to move against” the latter and the Mahdi Army in Basra. “Both the US and Iran, albeit at loggerheads over many issues, share an interest in backing” the Supreme Council against Sadr’s Mahdi Army.