U.S. and Iraqi forces battled enemy fighters in Sunni-controlled pockets of Iraq Monday, even as the military said the offensive to regain Fallujah from the insurgents was nearly over.

The worst reported fighting took place in the city of Baqouba on Monday, where explosions and gunfire broke out and more than two-dozen were killed there and in neighboring parts of the "Sunni Triangle."

U.S. and Iraqi troops and insurgents clashed in a belt running across central and northern Iraq. At least 27 people were killed Monday in Baqouba (search), neighboring Buhriz and Suwayrah, south of Baghdad.

Fighting was also reported in the ethnically mixed northern city of Mosul (search), Iraq's third-largest, and the Sunni insurgent stronghold of Ramadi, west of Fallujah.

Reuters reported Monday that an audiotape purportedly made by notorious Jordanian terrorist leader Abu Musab al-Zarqawi (search) was encouraging Iraqi insurgents to attack U.S. supply lines and forces elsewhere in Iraq.

"If it (the U.S. military) finishes Fallujah, it will move in your direction. Beware and deny it the chance to carry out this plan," said the speaker on the recording, posted on the Web.

The speaker, who was identified in the message as al-Zarqawi and whose voice resembled that of the Jordanian militant, said the Americans were overextended and "cannot expand" their operations.

"Shower them with rockets and mortars and cut all the supply routes," he urged. The authenticity of the tape could not be confirmed immediately.

In Baghdad after nightfall Monday, heavy explosions rocked the Green Zone — the barricaded neighborhood that houses the Iraqi government and U.S. Embassy. There were two huge plumes of smoke, and loudspeakers warned, "Take cover, take cover." But there was no immediate word on the blasts' cause.

In all, there have been 37 Americans and six Iraqis killed in the Fallujah operations and 320 Americans and 28 Iraqis wounded during the battle, Marine Col. Michael Regnar told FOX News.

U.S. officials estimated more than 1,200 insurgents have been killed in the week-old offensive, intended to secure a vital insurgent-held city so that national elections can go ahead in January as scheduled.

Of the injured Americans, 134 were treated and returned to the field, and two of the Iraqis wounded were treated and sent back to the field.

Coalition forces have detained some 1,052 enemy fighters and maybe more, Regnar told FOX. Some have been identified as foreign nationals, but the majority are Iraqis, according to Regnar.

Fallujah is "100 percent clear," Regnar told FOX, though the cleanup was continuing Monday.

"The city is secure ... and we can go anywhere we want," Regnar said

FOX News' Greg Palkot, embedded with the India Company 3rd Battalion 5th Marine Regiment, said that during a house-to-house searching central Fallujah, the unit encountered a group of about 10 fighters in one house and became engaged in a series of clashes with the insurgents.

Tanks and aircraft were called in to fire at the rebel-held location, Palkot reported, and Marines estimated that 21 enemy fighters were killed.

Col. Mike Schupp, the regimental commander leading Marines into battle, told Associated Press Television News on Monday that insurgents in southeastern sections of the city were not coming out to fight, but were laying in wait in groups of four or five inside buildings for U.S. forces searching house to house.

"They're pretty die hard," Schupp said. In the city's southern districts, "the enemy has nowhere to run. ... Their backs are against the wall. This is their last ditch effort."

Armed bands of men roamed Baqouba and Buhriz, about 35 miles north of Baghdad, attacking police stations and a nearby U.S. base. Militants killed Buhriz' police chief, Lt. Gen Qassem Mohammed, in an attack on his house, officials said. American aircraft dropped two 500-pound bombs on an insurgent position.

Outside Fallujah, a convoy of ambulances and relief supplies trying to enter the embattled city was forced to turn back because the fighting made it too dangerous, the head of the Iraqi Red Crescent said.

The Red Crescent and Red Cross have been unable to gain access to people inside Fallujah during more than a week of violence.

Even as fighting in the area continued, Iraq's interior minister declared victory in Fallujah.

"Fallujah is no more a safe haven for the terrorists and killers. This thing is over," Falah Hassan al-Naqib told reporters in Baghdad.

Prime Minister Ayad Allawi (search) announced Monday that the leader of a militant group behind the killing of some foreign hostages had been captured.

Moayad Ahmed Yasseen, leader of the group Muhammad's Army, was captured along with an unspecified number of his followers, Allawi said. Allawi did not say how many members of the group had been captured or what kidnappings the group had been involved in.

Also on Monday, Allawi's office confirmed that two of his female relatives who were kidnapped last week had been released. His cousin, Ghazi Allawi (search), 75, his cousin's wife and his cousin's pregnant daughter-in-law were abducted at gunpoint last Tuesday in western Baghdad's Yarmouk neighborhood.

"Yes, yes, the two women were released yesterday," said an Allawi spokesman. There was no word on the cousin, Ghazi Allawi.

On Sunday, U.S. Marines found the mutilated body of a Western woman as they searched for militants still holding out in Fallujah. The woman could not be immediately identified, but a British aide worker and a Pole are the only Western women known to have been taken hostage.

The disemboweled body of the woman was wrapped in a blood-soaked blanket on a street in Fallujah, Marines said.

Margaret Hassan (search), 59, director of CARE International in Iraq, and Teresa Borcz Khalifa (search), 54, a Polish-born longtime resident of Iraq, were abducted last month but the body could not be identified without further tests.

U.S. officials said Monday's Baqouba fighting started when insurgents attacked 1st Infantry Division soldiers with rocket-propelled grenades and small-arms fire near a traffic circle and police station.

U.S. troops started getting fire from a mosque, the U.S. military said. Iraqi security stormed the mosque and found rocket-propelled grenades, mortar rounds and other weapons and ammunition, the statement said.

Four 1st Infantry Division soldiers were wounded, although two of them returned to duty, the military said. Nine Iraqis, including one attacker, a policeman and seven civilians, were killed and 11 Iraqis were injured in the fighting, according to Mohammed Zayad of the Baqouba hospital.

On Monday, U.S. forces resumed heavy airstrikes and artillery fire, with warplanes making between 20-30 bombing sorties in Fallujah and surrounding areas. U.S. ground forces were trying to corner the remaining resistance in the city.

American forces had attacked a bunker complex Sunday in the city's south, where they discovered a network of steel-reinforced tunnels and underground bunkers. The tunnels connected a ring of facilities filled with weapons, an anti-aircraft artillery gun, bunk beds and a truck, according to a statement from the U.S. military.

"We found rooms, small rooms filled with blood, signs of wire to tie people up, things from the wall that people were, we believe, tied to, hung up on, some implements and instruments in these rooms," Col. Willard Buhl of the 3rd Battalion 1st Marines, told FOX News. "And my battalion has uncovered several of them, several."

Civilians seeking medical care were told through loudspeakers and leaflets to contact U.S. troops.

Attacks Escalate in Sunni Areas

Marine Maj. Gen. Richard Natonski, who designed the ground attack on Fallujah, said it had gone far more quickly than expected and that troops had fought their way across the city in just six days.

Natonski on Sunday described the ground war as a "flawless execution of the plan we drew up. We are actually ahead of schedule."

As fighting in Fallujah neared its conclusion, insurgent attacks appeared to escalate elsewhere in Sunni Muslim areas of central and northern Iraq.

Clashes between gunmen and Iraqi security forces early Monday in Suwayrah killed seven Iraqi police and national guardsmen and injured five others, police said.

Gunmen carried out near-simultaneous attacks on a police station and an Iraqi National Guard headquarters, police said. Two policemen and five National Guardsmen were killed.

The dead included Maj. Hadi Refeidi, the director of the Suwayrah police station.

Before the clashes, National Guardsmen opened fire at a booby-trapped car approaching their headquarters, killing the driver. The car was loaded with 880 pounds of TNT.

In the insurgent-heavy city of Ramadi, 70 miles west of the capital, heavy fighting erupted on Monday between militants and U.S. forces, residents said.

Sunni clerics at several mosques called on residents to kick out bands of armed men who have come from outside the city, claiming that the clashes inside Ramadi were impoverishing its citizens.

North of Ramadi, a U.S. convoy came under attack near the town of Baghdadi, with one Humvee destroyed, according to a Baghdadi police Lt. Mohammed Abdel Karim. There was no confirmation from the U.S. military about the incident.

In Mosul, where an uprising broke out last week in support of the Fallujah defenders, militants raided two police stations Sunday, killing at least six Iraqi National Guards and wounding three others.

One insurgent was killed and three others were wounded before Iraqi security forces regained control of both stations, witnesses said.

Insurgents also set fire to the governor's house, destroying it and damaging his car in northern Mosul. Provincial Governor Duraid Kashmoula also said the curfew will continue to be imposed on the city from 4 p.m. to 6 a.m. in the morning.

A gunbattle erupted Sunday between militants and U.S. troops in the main market in the northern town of Beiji, killing at least six people and wounding 20 others, according to witnesses.

One U.S. soldier was injured when a suicide bomber blew up his car near a U.S. convoy traveling between Balad and Tikrit, the military said. A Bradley fighting vehicle was damaged by a roadside bomb in Baghdad, injuring one soldier, the military said.

One Marine and an Iraqi soldier were hurt when five mortar shells struck a checkpoint outside Fallujah.

FOX News' Ian McCaleb, Greg Kelly, Greg Palkot, Catherine Donaldson-Evans and The Associated Press contributed to this report.