U.S. Marines launched an air and ground assault on Fallujah Thursday after representatives of the city refused to hand over top terrorist Abu Musab al-Zarqawi (search).
Late Thursday, residents of the city lying 40 miles west of Baghdad reported attacks from American planes and armored vehicles. Residents said the shelling was the most intensive since U.S. troops began weeks of "precision strikes" against al-Zarqawi's forces.
"It will be an uncomfortable night for the insurgents," 1st Lt. Lyle Gilbert, a spokesman for the 1st Marine Expeditionary Force, told FOX News shortly after the offensive began. "Safety, security and stability operation will take place in and around Fallujah."
Gilbert, speaking from Camp Fallujah (search ) — five miles away from the besieged city — added that U.S. forces did not decide on the action without input from the Iraqis.
"We did this at the request of the Iraqi government," he said. "We don't move until the interim Iraqi government tells us to."
However, Maj. Francis Piccoli, spokesman for the 1st Marine Expeditionary Force, said that Marines hadn't entered the city, although operations "in and around Fallujah" have been "intensified" with airstrikes as well as a sustained artillery barrage from outside the city.
Piccoli said two Marine battalions were engaged in the fight backed up by aircraft.
He would not say the attack was the start of a major campaign to recapture the city, saying he did not want to jeopardize any future operations.
Piccoli said the goal of the operation was to "disrupt the capabilities of the anti-Iraqi forces."
"Ultimately, the intent is to help the Iraqi government bring in democracy," he added. "As you bring in sustained security and stability, the Iraqi government can build on as they go into elections" in January.
U.S. officials believe al-Zarqawi's terrorist group, Tawhid and Jihad (search), is headquartered in Fallujah. The group purportedly claimed responsibility for two homicide bombings inside the heavily guarded Green Zone in Baghdad on Thursday, according to a statement posted on a Web site known for its Islamic content. The unprecedented attack killed at least six people, including four Americans, and wounded 20.
The U.S. military said its targets were linked to al-Zarqawi's terrorist network, including a building being used to store weapons, two safehouses used to plan attacks, several illegal checkpoints and a weapons cache.
At least five people were killed and 16 wounded, according to Fallujah General Hospital.
Fallujah residents said the Americans were attacking several areas with rockets, artillery and tanks. One resident said U.S. forces were using loudspeakers in the west of the city to urge Fallujah fighters to lay down their arms "because we are going to push into Fallujah."
Residents reached by telephone from Baghdad also said there were sharp clashes in the northern part of the city, which was a major battlefield during last April's Marine siege of Fallujah.
Iraqi Prime Minister Ayad Allawi (search) warned Wednesday that Fallujah must surrender al-Zarqawi and other foreign fighters or face military attack.
Abu Asaad, spokesman for the religious council of Fallujah, said that "handing over al-Zarqawi" was an "impossible condition" since even the Americans were unable to catch him.
"Since we exhausted all peaceful solutions, the city is now ready to bear arms and defend its religion and honor and it's not afraid of Allawi's statements," Asaad said in a live interview with Al-Jazeera television.
However, he used the Arabic word for "suspend," implying that the talks could resume later.
"We are not afraid of Ayad Allawi's statements or the American troops," Asaad said. "The government now is an (American) agent that is working to make this city easy for American troops to enter and do what they want."
Negotiations had been aimed at restoring government control to Fallujah, which fell under the domination of clerics and their armed mujahedeen followers after the end of the three-week Marine siege last April.
"Military operations didn't even stop when the negotiating delegation was in Baghdad," Asaad said. "Dozens are killed every day. Entire families have been eliminated."
The government made no comment about the breakdown of the Fallujah talks. However, national security adviser Qassem Dawoud said military operations against Fallujah "will continue" until the city "has been cleansed" of "terrorists."
Dawoud said he is hopeful the delegation will succeed in ridding the city of insurgents.
"I hope they can succeed and can take them away from Fallujah as soon as possible, or otherwise, we're preparing ourselves to smash them ... by military means," he said.
Fox News' Heather Nauert and Ian McCaleb and The Associated Press contributed to this report.