Battle for Falluja under way
U.S., Iraqi troops launch offensive to oust insurgents
A soldier takes aim at a target in Falluja, Iraq, Monday.
Battle for Falluja, bombings in Baghdad.
U.S. and Iraqi forces begin their assault on Falluja.
Interim Iraqi leader Ayad Allawi authorizes Falluja assault.
FALLUJA, Iraq (CNN) -- Thousands of U.S. and Iraqi troops have streamed into Falluja, beginning an all-out assault aimed at driving insurgents out of the city.
Pentagon officials said the operation involves more than 2,000 Iraqis and about 10,000 U.S. troops.
U.S. tanks fired 120-mm rounds into booby-trapped barricades for about an hour, igniting massive explosions. (Map of Falluja)
Military officials told CNN's Jane Arraf, embedded with troops, one of the initial goals has been achieved -- clearing a path through defenses in the northern part of the city.
The Army said U.S. airstrikes against one position killed an estimated 20 to 25 insurgents.
Four Marines were wounded in one engagement, a medic told embedded CNN journalist Karl Penhaul.
Penhaul reported hearing an almost constant barrage of explosions and machine gun fire and said that tracer fire was lighting the night sky. Insurgents could be heard chanting in Arabic: "God is great."
A target hit Monday, a battalion commander told Penhaul, was a position manned by about five insurgents armed with assault rifles who were acting as forward observers, trying to direct mortar fire against Marines outside the city.
Before the ground offensive began about 7 p.m. (11 a.m. ET), Falluja was pummeled for hours by airstrikes aimed at destroying suspected safe houses and other insurgent strongholds. Arraf said the forces cut power to Falluja before the start of the assault.
U.S. and Iraqi troops had surrounded the city as they awaited the order for a full attack.
(Gallery: Scenes from the field)
On Sunday, Iraqi forces seized a hospital, and U.S. Marines secured the two bridges over the Euphrates River on the west side of the city, according to a pool reporter. (Minor resistance as hospital seized)
Nearly 40 "terrorists" were killed in the hospital takeover and four foreign fighters -- two of them Moroccan -- were captured, said Iraqi interim Prime Minister Ayad Allawi. The nationalities of the other two were undetermined.
One of the bridges is where exuberant crowds of Iraqis hung the bodies of U.S. security contractors killed last spring. (Special Report: The Struggle for Iraq)
Allawi gives green light
Allawi said Monday he had given U.S. and Iraqi forces the green light to rid Falluja of insurgents, and he promised to restore law and order.
"We are determined to clean Falluja from terrorists," Allawi said at a news conference.
Allawi imposed a 6 p.m. (10 a.m. ET) curfew for Falluja and Ramadi, and closed Iraq's borders with Syria and Jordan to keep insurgents from escaping to other countries.
Allawi visited Iraqi troops as they waited to enter the city.
"First of all, this is our Iraq, and it is our duty to defend our country. We're counting on you to defend the country and regain its pride and its values," Allawi told them in Arabic. "I'm here to check on you and tell you that all of Iraq is with you."
Allawi announced a state of emergency in Iraq Sunday -- exempting the Kurdish north -- and told reporters the terrorists in Falluja "do not want a peaceful settlement."
U.S. and Iraqi forces hope to pacify Falluja in time for elections in January for a transitional national assembly.
Level of resistance unclear
Falluja is considered an insurgent command-and-control center for the rest of the country and a base for Abu Musab al-Zarqawi's terror network.
Military officials say 3,000 to 5,000 insurgents may be inside the city -- difficult terrain for urban warfare -- but they acknowledge many may have slipped away amid widespread reports that an offensive was coming.
U.S. Secretary of Defense Donald Rumsfeld acknowledged Monday that al-Zarqawi's whereabouts are uncertain. "I have no idea if he is there," Rumsfeld said.
In April, Marines attacked Falluja after four U.S. private security contractors were killed and mutilated, and the ensuing battles led to many deaths. The U.S.-led forces established an indigenous Falluja brigade to restore peace to the city, but in the summer, the brigade fell apart and insurgents solidified control there.
Success in Falluja will deal a blow to the terrorists in the country and should move Iraq further away from a future of violence to one of freedom and opportunity for the Iraqi people.
-- Defense Secretary Donald Rumsfeld
Falluja's population was estimated to be 250,000 to 300,000 before warfare escalated in the city earlier this year. Now, it is thought that 50,000 civilians remain.
American forces have pounded Falluja for months in an attempt to root out insurgents. U.S. warplanes, including AC-130 gunships, bombarded targets in recent days to weaken insurgent positions.
Senior officers with the Army's Task Force 2-2, part of the 1st Infantry Division, said they had seen no signs of suicide bombers of vehicle-borne improvised explosive devices they had expected to see, which they interpreted as possible signs that insurgents could be fleeing the city rather than choosing to fight.
In one incident, a task force intelligence officer said a Predator drone observed 15 to 20 insurgents running down a road away from advancing U.S. tanks. The insurgents were "neutralized" as they attempted to set up an ambush, the officer said.
From Washington, Secretary of State Colin Powell placed calls Monday to the foreign ministers of other countries in the region to discuss the operations in Falluja, spokesman Richard Boucher told reporters.
Also in Washington, Secretary of Defense Rumsfeld told reporters that the battle for Falluja was critical for the success of the U.S.-led war on Iraq.
About a report that some 500 Iraqi troops failed to show up for battle, Rumsfeld said, "I would characterize it as an isolated problem."
Rumsfeld downplayed the threat to the city's civilian population, saying U.S. forces are disciplined, well-trained and well-led.
"There aren't going to be large numbers of civilians killed and certainly not by U.S. forces," he said.
Other developmentsA British soldier with the Black Watch Regiment was killed in an attack Monday and two other soldiers were wounded, one of them seriously, the British Ministry of Defense said. The attack took place north of the Black Watch base camp at Camp Dogwood, south of Baghdad. Last week, three Black Watch members were killed by a suicide bomber. (Full story)A U.S. soldier died in a gunbattle in eastern Baghdad, the Combined Press Information Center said. An explosion damaged the front entrance of Baghdad's Yarmouk Hospital Monday. Police said they believe the hospital was targeted because Iraqi national guard troops were being treated inside. Two Marines died near Falluja on Monday when their bulldozer flipped into the Euphrates River in an apparent non-combat incident, military sources said. There were no further details.Fourteen insurgents died and nine others were arrested in an Iraqi police operation against insurgents in the Babil province town of Latifiya Sunday night. Police dressed in civilian clothes stormed a checkpoint being held by insurgents and freed a "number" of hostages, including two women, a police official said. The operation, involving about 100 police officers, netted a number of weapons, including machine guns, rocket-propelled grenades and stolen cars.
CNN's Karl Penhaul, Jane Arraf, Jamie McIntyre, Bessem Muhy, Cal Perry, Kevin Flower and Mohammed Tawfeeq contributed to this report.