NEAR FALLUJAH, Iraq (AP) - U.S. Army and Marine units pushed into the center of Fallujah on Tuesday, fighting with bands of guerrillas in the streets and searching house to house in a powerful advance on the second day of a major offensive to retake the insurgent stronghold.
A total of 16 Americans have been killed in the past two days across Iraq - including three killed in Fallujah combat on Tuesday, two killed by mortars near the northern city of Mosul and 11 others who died Monday, most of them as guerrillas launched a wave of attacks in Baghdad and southwest of Fallujah.
The 11 deaths were the highest one-day U.S. toll in more than six months.
As fighting raged in Fallujah, Prime Minister Ayad Allawi declared a nighttime curfew in Baghdad and its surroundings - the first curfew in the capital for a year - a day after a string of insurgent attacks in the city killed nine Iraqis and wounded more than 80.
Several heavy explosions hit central Baghdad Tuesday after nightfall, followed by the rattle of small arms fire.
Anger over the assault on the mainly Sunni Muslim city of Fallujah grew among Iraq's Sunni minority, and voices abroad - including the United Nations' refugee agency and the Red Cross - expressed fears over civilians' safety.
An influential group of Iraqi Sunni clerics called for a boycott of the election. The vote is being held "over the corpses of those killed in Fallujah," said Harith al-Dhari, director of the Association of Muslim Clerics.
If Sunnis refuse to vote on a large scale, it could wreck the legitimacy of the election, seen as vital in Iraq's move to democracy.
An estimated 6,000 U.S. troops and 2,000 allied Iraqi soldiers invaded the city from the north Monday night in a quick, powerful start to an offensive aimed at re-establishing government control ahead of the elections. The guerrillas fought off a bloody Marine offensive against the city in April.
On Tuesday, heavy street clashes were raging in Fallujah's northern neighborhoods. By midday, U.S. armored units had made their way to the highway running east-west through the city's center and crossed over into the southern part of Fallujah, a major milestone.
The military reported lighter-than-expected resistance in Jolan, a warren of alleyways in northwestern Fallujah where guerillas were believed to be at their strongest.
That could be a sign that insurgents left the city before the operation started or that the troops have not yet reached the center location to which the resistance has fallen back, Pentagon officials said in Washington.
U.S. officers said few civilians were trying to flee the city Tuesday. They said the bulk of the population of 200,000-300,000 left before the fighting and the rest were hunkered down because of a 24-hour curfew. U.S. troops were preventing most people from leaving, except in emergency cases. One funeral procession was allowed out of the city, U.S. officers said.
Before the Monday night attack, the U.S. military reported 42 insurgents killed, while Fallujah doctors reported 12 people dead. But since then, there has not been word of the Iraqi death toll.
U.S. forces cut off electricity to the city. Residents said they were without running water and were worried about food shortages because most shops in the city have been closed for the past two days.
"The north of the city is in flames. I can also see fire and smoke ... Fallujah has become like hell," Fadril al-Badrani, a resident in the center of Fallujah, said Monday night amid a heavy air and artillery barrage. He said hundreds of houses had been destroyed.
Allawi called on Fallujah's fighters to lay down their weapons to spare the city and allow government forces to take control, "The political solution is possible even if military operations are ongoing," his spokesman said.
The Fallujah campaign has seen five deaths reported by the U.S. military: three troops killed and 14 wounded on Tuesday, and two Marines who died in a bulldozer accident Monday.
In Fallujah's urban battles Tuesday, small bands of guerrillas - fewer than 20 - were engaging U.S. troops, then falling back in the face of overwhelming fire from American tanks, 20mm cannons and heavy machine guns, said Time magazine reporter Michael Ware, embedded with troops. Ware reported that there appeared to be no civilians in the area he was in.
On one thoroughfare in the city, U.S. troops traded fire with gunmen holed up in a row of houses about 100 yards away. An American gunner on an armored vehicle let loose with his machine gun, grinding the upper part of a small building to rubble.
Elsewhere, witnesses reported seeing at least two American tanks engulfed in flames. A Kiowa helicopter flying over southeast Fallujah took groundfire, injuring the pilot, but he managed to return to the U.S. base.
The once constant artillery barrages were halted, since so many troops were inside the city. U.S. and Iraqi forces surrounded a mosque inside the city that was used as arms depot and insurgent meeting point, the BBC reported.
Col. Michael Formica, commander of the 1st Cavalry Division's 2nd Brigade, said Tuesday that a security cordon around the city will be tightened to ensure insurgents dressed in civilian clothing don't slip out.
"As we tighten the noose around (the enemy), he will move to escape to fight another day. I do not want these guys to get out of here. I want them killed or captured as they flee," he said.
Guerrilla violence continued elsewhere. Hundreds of militants swarmed the streets of Ramadi, another insurgent stronghold 70 miles west of Baghdad. Gunfire rang out in the city center, and a destroyed car smeared with blood was seen.
Some 10,000-15,000 U.S. troops have surrounded Fallujah, along with allies Iraqi forces, according to the top U.S. commander in Iraq, Gen. George Casey. Commanders estimate around 3,000 Sunni fighters are in Fallujah, perhaps around 20 percent of them foreign Islamic militants.
The question of casualties is a major factor in the offensive. Reports of hundreds of people killed during the Marine offensive in April outraged Iraqis and forced the Marines to pull back - allowing guerrillas to only strengthen their hold on the city.
U.S. Defense Secretary Donald H. Rumsfeld insisted Monday, "There aren't going to be large numbers of civilians killed and certainly not by U.S. forces."
Allawi's government has also taken a prominent role in defending the assault - for which the prime minister gave the green light.
Still, it risks alienating Iraqis - particularly among the Sunni Arab minority. Industry Minister Hajim Al-Hassani, of the mainly Sunni Iraqi Islamic Party, quit the government Tuesday in protest.
Russia's Foreign Ministry warned that the attack could hurt the January election, saying the government is "concerned that the actions in this region not worsen the conditions in Iraq as a whole"
Arab League Secretary-General Amr Moussa said he hoped the violence "ends fast," adding that he was in touch with Iraqi officials. "No one can ever accept the way civilians are struck in Fallujah," he told reporters.
The U.N. refugee agency said Tuesday that it was "extremely concerned" about tens of thousands of people who fled ahead of the Fallujah fighting - many of them now living in tents.
And the International Committee of the Red cross said it was "very worried" that some wounded Iraqis have been unable to receive medical care because of the fighting.
