U.S. troops have "occupied" the entire city of Fallujah, leading Iraqi officials to declare on Saturday the mission "accomplished."

There were no more major concentrations of insurgents still fighting, U.S. military officials said. Artillery and airstrikes also ended at nightfall.

U.S. military officials said Saturday that American troops had now "occupied" the entire city of Fallujah and there were no more major concentrations of insurgents still fighting. Artillery and airstrikes also ended after nightfall.

Iraqi officials acknowledged that the two most wanted figures in the city — Jordanian terror mastermind Abu Musab al-Zarqawi and Sheik Abdullah al-Janabi — had escaped the fighting. At least 30 of Zarqawi's lieutenants had been killed, officials told FOX News.

But after nearly a week of intense urban combat, U.S. officers said resistance had not been entirely subdued and that it still could take several days of fighting to clear the final pockets.

At least 1,200 insurgents have been killed since the battle for Fallujah (search) began four days ago, U.S. military officials estimated.

Officials told FOX News on Saturday they believe about 400 enemy fighters may still be hiding out inside the Sunni Muslim stronghold, with 250 in the south and 150 in the north.

Twenty-five American troops were killed and about 170 wounded in the fighting. Officials said seven Iraqi soldiers were also been killed.

Grisly Discovery

U.S. Marines rescued two hostages being held captive in an apparent torture chamber, FOX News has learned. Soldiers were led to the chamber by a tip from one of the hostages' relatives and by the hostages' screams.

Iraq's national security adviser Qassem Dawoud said on national television that about 1,000 insurgents had been killed and another 200 captured during the Fallujah operation.

"We are just pushing them against the anvil," said Col. Michael Formica, commander of the 1st Cavalry Division's 2nd Brigade. "It's a broad attack against the entire southern front."

Marines in northern Fallujah were hunting for about a dozen insurgents dressed in National Guard uniforms after reports they were wandering the city.

"Any [Iraqi National Guard] or [Iraqi special forces] not seen with the Marines are to be considered hostile," Lt. Owen Boyce, 24, of Hartford, Conn., told his men.

Overnight, two city mosques were hit by airstrikes after troops reported sniper fire from inside. On Saturday, two Marines were killed by a homemade bomb southeast of Fallujah.

As the U.S. Army and Marines attacked inside Fallujah from the north, the Marines' 2nd Reconnaissance Battalion blocked insurgents from fleeing. U.S. officials estimate there are about 1,000-2,000 insurgents in the towns and villages around Fallujah who were not trapped inside the city during the U.S.-Iraqi siege, which began Monday.

A U.S. warplane dropped a 500-pound bomb to destroy an insurgent tunnel network in the city, embedded TV correspondent Jane Arraf reported.

U.S. officials said they hoped the latest surge would be the final assault on Fallujah, followed by a house-to-house clearing operation to search for boobytraps, weapons and guerrillas hiding in the rubble. U.S. and Iraqi officials want to restore control of Fallujah and other Sunni militant strongholds before national elections due by Jan. 31.

The fierce fighting has taken its toll on the Americans. More than 400 wounded soldiers have been taken to the U.S. military's Landstuhl Regional Medical Center in Germany, a hospital spokeswoman said.

A four-vehicle convoy of the Iraqi Red Crescent carrying humanitarian assistance arrived in Fallujah after the Iraqi and American troops allowed them to pass.

West of Baghdad on a highway stretching toward Fallujah, U.S. airstrikes and clashes between troops and rebels left four people dead and 29 others wounded, police and hospital officials said.

Dawoud estimated that 90 percent of Fallujah's residents evacuated before the assault.

With resistance in Fallujah waning, U.S. and Iraqi forces began moving against insurgent sympathizers among Iraq's hardline Sunni religious leadership, arresting at least four clerics and raiding offices of groups opposing the assault.

Meanwhile, the U.S. military said four American helicopters had been hit by insurgent ground fire in separate attacks near Fallujah. Their uninjured crews returned to base safely.

Flare-Up in Mosul

The most serious uprising outside of Fallujah occurred in Mosul (search), a city of about 1 million people 220 miles north of Baghdad, where insurgents targeted bridges, police stations and government buildings starting Thursday.

The 1st Battalion, 5th Infantry Regiment, a unit of the 25th Infantry Division, was ordered out of Fallujah and back to Mosul late Thursday.

On Saturday, a car bomb injured seven National Guardsmen, including two critically, as their convoy passed by in the eastern Nour district, said Radwan Hannoun of the Jumhuri Hospital.

Iraqi authorities requested reinforcements after police abandoned their posts. On Saturday, National Guardsmen, many of them ethnic Kurds, were seen patrolling parts of the city.

In a radio statement, Mosul Gov. Duriad Kashmoula blamed the uprising on "the betrayal of some police members." Kashmoula said more National Guard units had arrived to help restore order, and 40 insurgents had been killed in fighting.

Some witnesses reported seeing armed men wearing traditional Kurdish attire standing guard in at least three areas of the city. The Kurds are the most pro-American of Iraq's various ethnic and cultural groups.

Elsewhere in Iraq

Violence flared elsewhere in the volatile Sunni Muslim areas, from Hawija and Tal Afar in the north to Samarra and Ramadi in central Iraq.

In Baghdad, at least five heavy explosions rocked the city's center on Saturday night. Earlier, insurgents armed with rocket-propelled grenades attacked the Ministry of Education, a witness said. Iraqi police also clashed with militants.

In Washington, President Bush met with his top ally in the war, British Prime Minister Tony Blair, and warned that with Iraqi elections approaching, "the desperation of the killers will grow and the violence could escalate." But he said victory in Iraq would be a blow to terrorists everywhere.

Fallujah militants fought Marines to a standstill last April during a three-week siege, which the Bush administration called off amid public criticism over civilian casualties.

Many, if not most, of Fallujah's 200,000-300,000 residents fled the city before the assault. It is impossible to determine how many civilians not involved in the insurgency were killed.

Commanders said they believe 1,200-3,000 insurgents were holed up in Fallujah before the offensive.

FOX News' Bret Baier and The Associated Press contributed to this report.