Insurgents hammered central Baghdad on Sunday with one of their most intense mortar and rocket barrages ever in the heart of the capital, heralding a day of violence that killed 77 people nationwide as security appeared to spiral out of control.

At least 37 people were killed in Baghdad (search) alone. Many of them died when a U.S. helicopter fired on a disabled U.S. Bradley fighting vehicle as Iraqis swarmed around it, cheering, throwing stones and waving the black and yellow sunburst banner of Iraq's most-feared terror organization.

The dead from the helicopter strike included Arab television reporter Mazen al-Tumeizi, who screamed, "I'm dying, I'm dying," as a cameraman recorded the chaotic scene. An Iraqi cameraman working for the Reuters news agency and an Iraqi freelance photographer for Getty Images were wounded.

Maimed and lifeless bodies of young men and boys lay in the street as the stricken U.S. vehicle was engulfed in flames and thick black smoke.

Nearly 200 people were wounded throughout Iraq Sunday, more than half of them in Baghdad.

Strong detonations again shook the center of Baghdad after sunset. There were no reports of damage or casualties.

As the early morning barrage was under way in Baghdad, insurgents attacked the infamous U.S.-run Abu Ghraib (search) prison on the city's western edge. Several mortar shells exploded outside the complex about 6 a.m., and about 20 minutes later a pickup truck packed with artillery shells crashed through the chain-link fence on the outer perimeter.

Marines opened fire and the vehicle exploded before reaching the main security wall, killing the driver, a military statement said. Seven people were later arrested, it said.

Tawhid and Jihad, a militant group linked to Al Qaeda (search) and led by Jordanian terror mastermind Abu Musab al-Zarqawi (search), said it carried out Sunday's coordinated campaign of violence in Baghdad.

In an Internet statement, the group boasted that it holds the initiative in the Iraqi insurgency and possesses the "capability to surprise the enemy and hit its strategic installations at the right time and place."

The statement's source could not be verified, but the scope and intensity of the attacks raised serious questions about the state of security, which has deteriorated since the June 28 transfer of sovereignty to the interim Iraqi government.

In Basra, interim Prime Minister Ayad Allawi (search) vowed to pursue insurgents.

"We are adamant that we are going to defeat terrorism," Allawi said. "We intend to confront them and bring them to justice."

Interior Minister Falah Hassan al-Naqib suggested the attacks could be in response to a government operation against the Adel neighborhood of west Baghdad, an insurgent hotbed. However, the scope of the attacks suggested they had been in preparation for some time.

Secretary of State Colin Powell (search) acknowledged that the U.S.-led coalition faced a "difficult time" in Iraq but said the United States had a plan to quash the insurgency and bring those areas under control in time for national elections in January.

The insurgency "will be brought under control," Powell said on NBC's "Meet The Press." "It's not an impossible task."

Near Hillah, 60 miles south of Baghdad, three Polish soldiers were killed in an ambush — raising Poland's death toll in Iraq to 13 — and a bomb killed three Iraqi national guardsmen. A district police chief was killed in an attack in Baghdad's Yarmouk neighborhood.

Meanwhile, 10 people were killed and 40 were wounded in fighting in the insurgent stronghold of Ramadi, 70 miles west of Baghdad, said hospital director Abdel Munim Aftan.

Three American soldiers and two Iraqi civilians were wounded Sunday when a suicide driver blew up his car next to a U.S. Army convoy on the road to Baghdad International Airport, American sources said. The vehicle was one of seven car bombs reported Sunday in Iraq, two of which did not explode, the sources said.

Powell did not elaborate on the plan for addressing the insurgency, but senior U.S. officials in Iraq have spoken of a multi-pronged strategy involving overtures to tribal leaders, economic incentives and the use of force as the best way to prevail against the resistance.

Rockets and mortar shells began raining down before dawn on the Green Zone, headquarters of the Iraqi government and its U.S. allies, and other parts of central Baghdad. As the shelling continued after sunrise, U.S. troops backed by armored vehicles moved into the streets searching for the attackers.

A Bradley fighting vehicle rushing down Haifa Street, a major traffic artery near the Green Zone, to assist a U.S. patrol was disabled by a car bomb about 6:50 a.m., the U.S. military said. Two Bradley crewmen were wounded by the bomb and four were injured by grenades and small-arms fire as they fled the vehicle, the military said.

Jubilant fighters, curiosity seekers and young boys swarmed around the burning vehicle, dancing, cheering and hurling firebombs. Several young men placed a black and yellow banner of Tawhid and Jihad in the barrel of the Bradley's main gun.

Fearing the crowd would loot the vehicle of weapons and ammunition, American soldiers called for air support, and as U.S. Army helicopters flew over the burning Bradley "they received small-arms fire from the insurgents in vicinity of the vehicle," a military statement said.

The helicopters "fired upon the anti-Iraqi forces and the Bradley preventing the loss of sensitive equipment and weapons," the statement said. "An unknown number of insurgents and Iraq civilians were wounded or killed in the incident."

Iraq's Health Ministry said 13 people were killed and 61 wounded on Haifa Street, though it was unclear how many were killed by the helicopter strike. Scattered shoes, pools of fresh blood and debris littered the street.

"We were standing near the destroyed vehicle when the helicopter started firing, so we rushed to safety in a nearby building," Alaa Hassan, 24, said from his hospital bed. "I went back to the scene to help the wounded people when the helicopter fired again and I was hit in the chest."

Twelve more people died and 41 were injured in other violence across the city Sunday, the Health Ministry said.

Elsewhere, gunmen attacked a group of policemen in the northern city of Mosul, killing one and wounding seven, police said.

Also in the north, three security officers were wounded when attackers opened fire as they stood guard near the Dibis oilfields northeast of Kirkuk. Two others were injured in a drive-by shooting west of Kirkuk, said Maj. Gen. Anwar Mohammed Amin of the Iraqi national guard.

Security officers guarding the oil-rich Kirkuk area have repeatedly been targeted by militants, who have blown up dozens of pipelines in a bid to disrupt reconstruction efforts and undermine the U.S.-backed interim government.