Getting your Trinity Audio player ready...

Shiite militants pressed their insurgency into central Baghdad on Tuesday, shutting down much of the capital with threats of attacks against government institutions, while U.S. forces in the holy city of Najaf tightened their siege on radical militiamen and warned residents to flee.

In Baghdad, members of cleric Moqtada Sadr’s al-Mahdi Army left their stronghold in the Sadr City slum, setting up temporary checkpoints in parts of the city and briefly occupying a police station in a nearby neighborhood. Many of the city’s shops were closed, as insurgents had urged.

F-16 fighter planes screeched over the capital throughout the day, dropping flares as a precaution against heat-seeking missiles.

In Najaf, black smoke rose over parts of the city on the sixth day of fighting between Shiite militia members and U.S. troops backed by Iraqi security forces. A large fire broke out at a hotel 300 yards from the Imam Ali mosque, the holiest site in Shiite Islam.

U.S. Marines and members of the Iraqi National Guard drove through Najaf, appealing through loudspeakers for residents to leave the area around the shrine, which militia members are using as a base, said Sharon Walker, a civilian spokeswoman for the U.S. military in Baghdad. Iraqis and U.S. Marines prepared for a possible assault on the mosque.

Marines in Bradley Fighting Vehicles attacked pockets of militiamen in Najaf’s huge cemetery near the shrine, and helicopters provided support, firing rockets, witnesses said.

Parts of Najaf were deserted, but some motorists ventured into the streets. Despite the danger, a few children rode their bicycles.

Marines said the fighting was lighter than in previous days, but they didn’t expect the relative calm to last.

“I think it’s the quiet before the storm,” Marine Maj. David Holahan told The Associated Press.

Neither side showed any signs of stepping back from the brink of a potentially explosive battle at the shrine.

Though senior military officials say they are well aware that an attack on the shrine could rouse anti-American passions among the nation’s Shiite majority, they have emphasized that the interim Iraqi government has authorized an assault.

Prime Minister Ayad Allawi issued a statement late Tuesday, saying the interim government “decided to hit . . . with an iron fist all these desperate criminals that are attempting to hinder the bright future of the people of Iraq.”

The confrontation follows the breakdown of a 2-month-old truce between Sadr and U.S. forces. U.S. occupation authorities negotiated the cease-fire in June in hopes of avoiding a Shiite backlash as they were assembling the interim government.

But the militia never disbanded or left Najaf, and its harassment of Iraqi police was seen as a provocation of the new government.

“It is a very severe test for us, but we are willing to take it on,” said Sabah Kadhim, a senior adviser to the interior minister. “We cannot have this because, quite frankly, the Iraqi people cannot tolerate it anymore.”

But the prospect of a decisive confrontation at the Iman Ali mosque troubles many Iraqis.

“I hope they will find a peaceful solution that satisfies everybody,” said Adnan Mohammed, 60, a real estate agent on the outskirts of Sadr City.

`Sons of one country’

“We are all the sons of one country, and the blood that is being spilled belongs to Iraqi people. Sadr is an Iraqi and he has the right to express himself, though he should do it in a way that respects the safety of ordinary people.”

Renewed clashes between U.S. forces and Sadr loyalists were reported in Baghdad despite a new 4 p.m. to 8 a.m. curfew in Sadr City, which is named for the cleric’s late father.

The U.S. military blocked entrances to the slum. Black smoke hung over the area, apparently from burning tires used for rebels’ roadblocks.

Sadr’s al-Mahdi militia also imposed its own curfew, starting at 1 p.m., and instructions broadcast from mosques in Sadr City told citizens to stay home. Witnesses said militia members attempted to enforce the curfew beyond the slum neighborhood in several Baghdad districts.

Hassan Sameer Hassan, a 15-year-old who was selling cigarettes in one of the capital’s commercial districts, said he saw armed black-clad men jump out of a car, order local shopkeepers to shutter their shops and then set fire to two tires.

After they left, the shops reopened, he said.

Many Baghdad businesses already were closed because of a warning issued the previous day by an unknown group called the Brigade of Divine Wrath.

The increasing danger on the streets was underscored when the Interior Ministry confirmed that Brig. Gen. Raed Mohammed Khudai, the commander of police patrols in eastern Baghdad, was kidnapped Monday by militia members.

A Jordanian businessman also was kidnapped in Baghdad by an unknown group demanding a $250,000 ransom, Jordan’s Petra news agency reported Tuesday.

Fewer mortar attacks

Mortar attacks, which increased in recent days during the new fighting, appeared to be diminishing. The U.S. military said four mortars landed Tuesday morning in downtown Baghdad, just north of the fortified Green Zone where the U.S. Embassy and Iraqi administration offices are located.

In a potential rift, Danish troops in Iraq have stopped handing over prisoners to British commanding forces because the Iraqi government reinstated capital punishment, the Defense Ministry said Tuesday.

Denmark is obliged under the European Convention on Human Rights not to extradite prisoners who could face the death penalty, which is banned in the European Union. But Britain insisted Tuesday that European human-rights conventions don’t apply in Iraq, and that detainees must be handed over to the Iraqis.