Facing a major assault in Fallujah (search), insurgents struck back Saturday with homicide car bombs, mortars and rockets across a wide swath of central Iraq, killing over 30 people and wounding more than 60 others, including nearly two dozen Americans.

The attacks could have been aimed at relieving pressure on Fallujah, where about 10,000 American troops are massing for a major assault. Web site postings late Saturday claimed responsibility for several attacks in the name of an Al Qaeda-linked group believed holed up in Fallujah.

U.S. jets pounded Fallujah early Saturday in the heaviest airstrikes in six months — including five 500-pound bombs dropped on insurgent targets. Residents reported U.S. artillery fire late Saturday in southern parts of the city.

The deadliest attacks Saturday occurred in Samarra (search), a city 60 miles north of Baghdad that U.S. and Iraqi commanders have touted as model for pacifying restive Sunni Muslim areas of the country.

Insurgents in Samarra stormed a police station, triggered at least two homicide car bombs and fired mortars at government installations. One of the car bombs, targeting the mayor's office, used a stolen Iraqi police vehicle, the U.S. military said.

Twenty-nine people, including 17 police and 12 Iraqi civilians, were killed throughout the city, the U.S. military said. Arabic language television stations said more than 30 died as gangs of insurgents roamed the city, clashing with American and Iraqi forces.

The dead included the local Iraqi National Guard (search) commander, Abdel Razeq Shaker al-Garmali, hospital officials said. Forty other people, including 17 policemen, were injured, the military said.

U.S. military vehicles roamed through the besieged city using loudspeakers to announce an indefinite curfew starting at 2 p.m. Saturday. American warplanes and helicopters roamed the skies.

Elsewhere, 16 American soldiers were wounded Saturday when a homicide bomber using an Iraqi police car rammed their convoy in Ramadi, a major city in the volatile Sunni Triangle, U.S. officials said. They gave no further details, citing security.

Three other Americans were wounded when a car bomb exploded near the entrance to Baghdad International Airport. One Iraqi was killed and another injured, the U.S. military said. Three Humvees were heavily damaged, witnesses said.

Two Marines were injured by a car bomb near a Fallujah checkpoint, and a U.S. soldier was wounded when a roadside bomb exploded south of Fallujah. Explosions rattled the center of Baghdad through the night Saturday.

In Web postings, the Al Qaeda affiliate group of Abu Musab al-Zarqawi (search) claimed responsibility for the attacks in Samarra, Ramadi and Baghdad. The claims could not be verified, but U.S. officials believe al-Zarqawi's group uses Fallujah as a base.

Samarra, an ancient city of gold-domed mosques that once served as the capital of a Muslim empire extending from Spain to India, was recaptured from Sunni Muslim insurgents in September and was touted as a model for restoring government control to other areas formerly under guerrilla domination.

U.S. and Iraqi forces hope to use the same techniques if they drive Sunni militants from Fallujah. American commanders have assembled a force of Marines, Army soldiers and U.S.-trained Iraqi fighters around Fallujah, a major insurgent base 40 miles west of Baghdad.

They are awaiting orders from interim Prime Minister Ayad Allawi to launch an all-out assault.

Col. Gary Brandl voiced his troops' determination:

"The enemy has got a face. He's called Satan. He's in Fallujah and we're going to destroy him."

However, the violence in Samarra underscored the difficulty of maintaining civilian authority in Sunni areas even after the worst of the fighting ebbs.

"I cannot claim that entering Fallujah will end the terrorist attacks in Iraq," Iraq's national security adviser, Qassem Dawoud, told Al-Arabiya television. "But I can say that we will deal with a very big pocket of terrorism in Iraq and we will uproot it. This pocket forms the backbone and the center for terrorists in other areas in Iraq."

Elsewhere, gunmen killed a former official of Saddam Hussein's intelligence service in Baquouba, 55 kilometers (35 miles) northeast of Baghdad, police said. The assailants stopped a car carrying former Lt. Col. Abdul Sattar al-Luheibi, ordered him out of the car and gunned him down in front of his 13-year-old son.

U.S. and Iraqi authorities hope to curb the insurgency so that national elections can be held by the end of January. However, U.N. Secretary-General Kofi Annan and others have warned that a military offensive could trigger a wave of violence that would sabotage the ballot.

The influential Sunni clerical Association of Muslim Scholars has threatened to call a boycott if Fallujah is attacked. A public outcry over civilian casualties prompted the Bush administration to call off a siege in April, after which Fallujah fell under control of radical clerics.

"The experience that occurred in Samarra is now being repeated again in Fallujah, and we can see that nothing was achieved in Samarra," Ayad al-Samaraei of the Sunni-led Iraqi Islamic party told Al-Jazeera television. "The situation is still as it was before" in Samarra.

In an open letter to the Iraqi people posted Saturday on the Internet, 26 Saudi scholars and religious preachers said that armed resistance against American troops and their Iraqi allies was a "legitimate right."

The scholars issued a fatwa, or religious edict, prohibiting Iraqis from offering any support for military operations carried out by U.S. forces against militant strongholds.

"Fighting the occupiers is a duty for all those who are able," said the letter dated Friday. "It is a jihad to push back the assailants ... Resistance is a legitimate right. A Muslim must not inflict harm on any resistance man or inform about them. Instead, they should be supported and protected."

U.S. intelligence estimates there are about 3,000 insurgents dug in behind defenses and booby traps in Fallujah, a city of about 300,000 which has become a symbol throughout the Islamic world of Iraqi resistance to the U.S.-led occupation.

Allawi, a secular Shiite Muslim with strong ties to the CIA and State Department, has demanded that Fallujah hand over foreign extremists, including al-Zarqawi and his followers, and allow government troops to enter the city. Al-Zarqawi's group is responsible for numerous car bombs and beheading several foreign hostages.

Military planners believe there are about 1,200 hardcore insurgents in Fallujah — at least half of them Iraqis. They are bolstered by insurgent cells with up to 2,000 fighters in the surrounding towns and countryside.

Iraqi authorities have closed a border crossing point with Syria, and U.S. troops have sealed up the main highway into Fallujah.