The usual teeming traffic in Sadr City, Baghdad's Shiite enclave, vanished Wednesday. Buses stopped running and shops closed. Only the intrepid motorist or occasional scurrying resident ventured out on streets patrolled by Moqtada al-Sadr's militiamen and marked by burning tires and roadblocks.
Residents and Mahdi Army militants alike appeared to be bracing for a coming battle, guarding against US and Iraqi forces advancing to stop the rockets allegedly fired from Sadr City that hit the Green Zone again Wednesday for the third day since Sunday.
Although it's in Basra, the oil-rich southern city, where the Mahdi Army and Iraqi forces were locked in a bitter fight for a second day, killing at least 55, many in Baghdad fear that clash will trigger a new battle in Mr. Sadr's Baghdad stronghold. Already there were reports by US-funded Al Hurra TV, citing hospital sources, that at least 20 people have been killed and 140 wounded in sporadic clashes in Sadr City since Tuesday.
Now, in a place where the US has done battle many times before, a sense of siege and helplessness has replaced some of the flickers of optimism that emerged over the past few months as a result of improved security made possible by the US surge and the Mahdi Army's seven-month cease-fire, which now looks to be shattered.
"We are yet again caught between two fires and we the citizens always pay the price of the feuding by the political leaders," said a man who gave his name as Abu Muthana. He stood in front of a row of shuttered shops, including his own, off Beirut Square on the edge of Sadr City. The district's shops closed in obedience to a call for protest issued by Sadr's movement.
In the nearly empty square, Muhammad Karim rushed on his bicycle to get his brother, Majid, who was manning a modest tea stand.
"You have to lock up, come on, all hell is going to break loose soon," Muhammad told his brother, who grudgingly padlocked the battered metal cabinet that serves as his teashop and shuffled away.
Nearby, another resident, Nada Makhallad, walked her son, Ayman, back home because his elementary school was shut down. She was on the verge of tears.
She had to beg a pharmacist to come and open up so she can get medicine for her ailing mother.
"We live in a state of fear. I want to get out," said Ms. Makhallad, adding that she's going to try to find a way to leave Baghdad soon to join her husband working in Lebanon now.
Another resident, who spoke on condition of anonymity for fear of retribution, said he picked up three bodies of employees at Baghdad Airport allegedly shot dead by militiamen after challenging their orders.
Across the Shiite enclave, home to almost 3 million people, US soldiers – some on foot and others in Stryker combat vehicles and Humvees – were out in force at all the major entrances, especially next to Iraqi Army checkpoints.
Fallah (Farmer) Street and all other major thoroughfares were blocked by militiamen with rocks. Iraqi National Police in the area warned that militiamen planted bombs all along these roads to keep US and Iraqi forces out. Militiamen have also reportedly ordered all residents to turn off their generators.
Several other Iraqi government checkpoints were attacked by militiamen with mortars and gunfire. Heavy clashes pitted US and Iraqi forces against the militia for almost an hour in the northeastern neighborhood of Shaab, according to residents and an Interior Ministry official there.
As night fell, the sound of heavy gunfire and explosions echoed throughout Sadr City.
"Much of the indirect fire that has been directed towards neighborhoods here in Baghdad has emanated from … Sadr City in particular. We do have a responsibility to work with Iraqi security forces to interdict the ability for the … cells to continue doing what they are doing … and to enforce the rule of law against criminal activities and illegal armed groups that might be seeking to impose their own intimidation," said Maj. Gen. Kevin Bergner, a spokesman for US-led forces in Iraq, when asked about the enforced US and Iraqi Army ring around Sadr City.
During his press conference, and shortly afterward, several rocket or mortar explosions echoed inside the heavily protected Green Zone, home to top US and Iraqi officials.
Three Americans were seriously injured in the attacks, US Embassy spokeswoman Mirembe Nantongo said.
At least eight Iraqis also were killed after rounds fell short in several areas of Baghdad.
An American financial analyst working for the Embassy was killed in a rocket attack Sunday on the Green Zone.
In Basra, a showdown between government forces and the Mahdi militiamen looms. On Wednesday, the Iraqi government gave a 72-hour ultimatum to the Mahdi Army militia to lay down its weapons or face an all-out assault.
Some American elements were embedded as advisers and "transition teams" with Iraqi units fighting in Basra, said a US military spokesman.
Top political and clerical leaders allied to Sadr have all accused the Shiite-led government of Prime Minister Nouri al-Maliki and particularly its Islamic Supreme Council of Iraq and Badr Organization factions of seeking to finish off the movement in the south and Baghdad with the help of the Americans.
Mr. Maliki remained in Basra to supervise the crackdown against the spiraling violence between militia factions vying for control in the city located near the Iranian border.
Officials in Sadr's headquarters in Najaf, speaking on condition of anonymity because of the sensitivity of the issue, said the anti-US cleric had sent local representatives to ask Maliki to leave Basra and to resolve the problems peacefully. The aides also told the government no negotiations could be held until Iraqi reinforcements withdrew from the city.
• Material from the Associated Press was used in this report.