Insurgents, meanwhile, ambushed and killed nine Iraqi policemen as they were returning home from a training course in Jordan.
Throughout the day, the crackle of automatic weapons fire and the thud of artillery echoed across Fallujah, 40 miles west of Baghdad, as fighting between American troops and insurgents raged on the eastern and southern edges of the city, witnesses said.
Clashes blocked the main road leading to Baghdad, and plumes of smoke rose above the flat-roofed houses in the city's Askari and Shuhada neighborhoods in eastern and southern Fallujah.
Witnesses said a Humvee was seen burning in the eastern edge of the city, and hospital officials reported three civilians were killed. There was no casualty report from the U.S. military.
American forces have stepped up attacks around Fallujah since peace talks between the Iraqi government and Fallujah clerics broke down last Thursday after city leaders rejected Prime Minister Ayad Allawi's demand to hand over "foreign terrorists," including Jordanian-born extremist Abu Musab al-Zarqawi.
Fallujah clerics insist al-Zarqawi, whose Tawhid and Jihad movement has claimed responsibility for multiple suicide car-bombings and hostage beheadings, is not in the city. Fallujah fell under the control of hardline Islamic clerics and their armed followers after U.S. Marines lifted a three-week siege in late April.
On Sunday, Allawi's government renewed its call for Fallujah to surrender al-Zarqawi and others, saying their presence in "some areas and cities" is "something the government cannot accept or tolerate."
"We call upon the sons and tribes of Fallujah to immediately expel foreign terrorists and evacuate all the city's neighborhoods from these murderers and their criminal supporters who want to hamper plans of reconstructing Iraq," National Security Adviser Qassem Dawoud said in a statement.
Dawoud said "the door is still open before any initiative or effort to avoid having to use the military option."
Elsewhere, police said Sunday that nine Iraqi policemen returning from training in Jordan were ambushed and killed Saturday in Latifiyah, an insurgent stronghold 25 miles south of Baghdad. The attackers escaped. Latifiyah is part of a belt of towns just south of the capital where kidnappings and ambushes have been common.
Along the Syrian border, overnight clashes between U.S. troops and insurgents left four people dead and 13 others wounded, Dr. Wael al-Duleimi said Sunday from the border town of Qaim. The city is a hotbed of insurgent activity and is believed to be a major route for smuggling weapons and fighters into Iraq.
In other developments:
In hopes of sparing Fallujah further violence, the city's clerics have offered to resume peace talks if the Americans stop their attacks. But the talks have deadlocked over the alleged presence of Zarqawi and other foreign fighters.
"We are still ready to go back to the talks and open new channels of dialogue," said negotiator Abdul Hamid Jadou. But he said Allawi is "responsible for each drop of blood being spilled in Fallujah. This government sided with the Americans in bombing the innocent people who are fasting in Ramadan."
As the Iraqis seek a peaceful end to the Fallujah standoff, the U.S. military is believed to be drafting plans for an all-out assault on the city if negotiations fail.
Iraqi officials hope that Fallujah leaders can be persuaded to negotiate a deal similar to one struck with Shiite radical cleric Muqtada al-Sadr to end clashes in the Sadr City district of Baghdad. Under the deal, al-Sadr's fighters have been turning in weapons for cash.
On Sunday, a mortar shell exploded at a sports stadium about 15 minutes before Allawi was to arrive to inspect the guns-for-cash program. The itinerary was quickly changed and Allawi visited several other sites before arriving at the stadium.
"I am very thrilled and pleased that things are moving in the right direction and arms are being surrendered to the Iraqi government," he said.
Allawi also called on Iraqis throughout the country — whether in Basra, Nasiriyah, Fallujah, Ramadi or Mosul — to surrender their weapons and to respect the rule of law and to be part of the political process.