BAGHDAD, Iraq (AP) – The Iraqi government formally launched a long-awaited security crackdown in Baghdad on Wednesday, with U.S. and Iraqi troops stepping up patrols, establishing new checkpoints and randomly searching cars to stop the violence in the capital.

Prime Minister Nouri al-Maliki said the sweep, code-named Operation Imposing Law, would target those “who want to continue with rebellion.”

There were conflicting reports, meanwhile, about the whereabouts of Muqtada al-Sadr, whose militia have been blamed for some of the worst sectarian killings in the past year, after a U.S. official said the radical Shiite cleric had fled to Iran ahead of the security operation.

Maj. Gen. William Caldwell, the chief U.S. military spokesman, insisted that al-Sadr had left the country, although he declined to comment on the reasons or give other details.

“We will acknowledge that he is not in the country and all indications are in fact that he is in Iran,” Caldwell told reporters in Baghdad.

But several of the cleric’s supporters denied the reports, with one official saying the cleric had met with government officials late Tuesday in the Shiite holy city of Najaf, where he has his headquarters.

Lawmaker Nassar al-Rubaie, the head of Sadrist bloc in parliament, also insisted al-Sadr had not left the country.

“The news is not accurate because Muqtada al-Sadr is still in Iraq and he did not visit any country,” lawmaker Nassar al-Rubaie, the head of Sadrist bloc in parliament, told The Associated Press.

Also on Wednesday, CNN reported that a Shiite militant group has issued a video of Iraqi-born U.S. Army translator Ahmed Qusai al-Taayie, a 41-year-old reserve soldier from Ann Arbor, Mich., who was abducted by gunmen on Oct. 23.

The video was broadcast by CNN and it was unclear when it was made. Al-Taayie’s uncle identified him from the video, the network said. The video did not immediately turn up in an AP search of militant Web sites.

Caldwell said officials were aware of the video and were analyzing a copy of it.

A U.S. soldier died Wednesday after coming under small arms fire a day earlier from insurgents while on patrol north of Baghdad, the military said. Separately, another soldier died Tuesday in a non-combat-related incident that is under investigation, it said.

The deaths raise to at least 3,128 members of the U.S. military who have died since the war began in March 2003, according to an AP count.

The U.S. military announced last week that the clampdown had already begun, but Iraqis had seen little evidence of that before Wednesday. President Bush has committed 21,500 more Americans to the operation, which is expected to involve a total of 90,000 Iraqi and U.S. soldiers.

As the new checkpoints were set up in the city of 6 million of people, huge traffic jams developed and cars were forced to zigzag through soldiers’ positions and barricades.

Dozens of people left their buses to cross the central Sinak Bridge on foot rather than wait for the vehicles to move through the jams. At one checkpoint, Iraqi troops stopped a convoy of three white SUVS that are commonly used by Iraqi government officials and checked their identification.

Al-Maliki discussed the security plan during a meeting with officials in the Shiite holy city of Karbala, 50 miles south of Baghdad.

“We have started today the new security plan. And we warn everyone who runs against it: Now we are ready to impose law on all those who want to continue with rebellion,” he said. “Baghdad operations started today under code name ‘Imposing Law.”‘

“By God willing, the new plan will have fruitful outcomes, not because of the use of force but because of those who declare their love to Iraq and its people,” he said before going to the entrance of the Imam Hussein mosque to address thousands of supporters massed in the streets.

The pep talk came a day after the Iraqi commander of the Baghdad security crackdown, Lt. Gen. Abboud Qanbar, announced that Iraq will close its borders with Syria and Iran and ordered the return of unlawfully seized homes as part of the drive to end the violence that has threatened to divide the capital along sectarian lines.

Despite the stepped-up security, a parked car bomb struck a predominantly Shiite district elsewhere in central Baghdad, killing four civilians and wounding 10, police said.

In the western city of Ramadi, a suicide car bomber struck a police station, killing at least eight policemen and wounding seven, police said. The Warar station had just been rebuilt three months ago as part of reconstruction efforts in the volatile capital of Anbar province, an insurgent stronghold west of Baghdad.

A suicide car bomber also targeted an Iraqi army patrol in the northern city of Mosul, killing one soldier and four civilians and wounding 20 other people, police Brig. Abdul Karim al-Jubouri said.

Qanbar said Baghdad’s nighttime curfew would be expanded by an hour, from 8 p.m. to 6 a.m., and permits allowing civilians to carry weapons in public would be suspended during all of the operation, which he suggested could last weeks.

The commander also said those who had occupied homes of displaced families would be given 15 days to return the properties to the original owner or prove they had permission to be there.

The general did not say when the borders would close, but another official said it was expected in two days. The official, who spoke on condition of anonymity because he was not authorized to speak to journalists, added that the borders would only partly reopen after the 72-hour closing.

The United States has long charged that Iran and Syria let extremists use their territory to slip into Iraq to attack U.S. and Iraqi forces as well as civilians.

Iraqi authorities have routinely echoed the U.S. charges against Syria, but they rarely make that claim about Iran, which has close ties with Iraq’s Shiite-led government.

The campaign is widely seen as possibly the U.S. military’s final attempt to calm the city. It will be the third attempt by U.S. forces and their Iraqi allies to end violence in Baghdad since al-Maliki took office in May 2006.

Qanbar said he would report to al-Maliki weekly to discuss progress in the operation.

His address suggested Iraqi authorities plan to exercise wide powers while waging the crackdown. A criminal court, for example, will hold emergency hearings on cases such as murder, theft, rape, kidnapping, damaging public property and the possession and transfer of arms and ammunition, he said.

Qanbar, a Shiite and a veteran of the 1991 Gulf War when he served in Saddam Hussein’s army, said security forces also plan to monitor mail, parcels, telegrams and wireless communication devices during the operation.

He said security forces would try to avoid intruding in places of worship, but added that they would do so in “extreme emergencies when it is feared that these places pose a threat to the lives of citizens or if they are used for unlawful purposes.” U.S. and Iraqi authorities have often said Sunni Arab insurgents use mosques to store arms or fire at troops.

Al-Maliki urged unity in ending the violence.

“We will not kneel down nor succumb no matter how much the process takes blood from us,” he said while some people on the street chanted anti-American slogans. “By targeting civilians, the terrorists think that they can stop our progress, but our fingers are on the trigger and all the Iraqi people … are rising to rebuild the new Iraq.”

Some in the crowd waved photos of al-Maliki signing the execution order for former leader Saddam Hussein.

“We welcome this visit of the man whose blessed hands have approved the execution of the tyrant Saddam,” said 36-year-old Mohammed Hussein. “We wish him all the best and we wish that God will help him to achieve stability and security for our country. We also wish that he can provide services and job opportunities.”

AP-ES-02-14-07 1437EST