Car bombs killed at least a dozen people in Baghdad and another major city Tuesday as pressure mounted on interim Prime Minister Ayad Allawi (search) to avert a full-scale U.S. attack on the insurgent stronghold Fallujah.

There was no word on an American and two other foreigners abducted Monday in Baghdad, although the kidnappers freed two Iraqi guards also captured in the attack.

Early Wednesday, Iraqi police said a Lebanese-American contractor was kidnapped from his Baghdad home. Lt. Col. Maan Khalaf said the unidentified contractor, who works for the U.S. Army in the Green Zone, was snatched from his home in Mansour neighborhood around midnight.

Khalaf said armed gunmen knocked at the door to his home and seized him when he answered the door. There were apparently no guards at the time of the attack and no gunfire, he said.

Meanwhile, kidnappers of aid worker Margaret Hassan (search) threatened to turn her over to Al Qaeda-linked militants notorious for beheading hostages unless Britain agreed within 48 hours to pull its troops from Iraq, Al-Jazeera television reported Tuesday.

Al-Jazeera broadcast a portion of a video showing a hooded gunman, and without sound. No group has claimed responsibility for Hassan's kidnapping and the broadcast showed no sign of any banner identifying who held her.

In London, Prime Minister Tony Blair's (search) office and the British Foreign Office both declined to comment on the reported demand. Britain has 8,500 troops in Iraq, the second-largest contingent after the United States.

In northern Iraq on Tuesday, saboteurs blew up an oil pipeline and attacked an oil well, violence that is expected to stop oil exports for the next 10 days, Iraqi oil officials said. Iraq's oil industry, which provides desperately needed money for reconstruction efforts, has been the target of repeated attacks by insurgents.

At least eight people, including a woman, died early Tuesday when an explosives-laden car slammed into concrete blast walls and protective barriers surrounding the Education Ministry and exploded in Baghdad's Sunni Muslim district of Azamiyah.

Ten others were injured, including a 2-year-old girl, according to Al-Numan Hospital. Officials at Baghdad Medical City Hospital reported two more deaths and 19 injured. Dr. Raed Mubarak said he was unsure whether some of the wounded were transferred from other hospitals.

In Mosul, 225 miles northwest of Baghdad, a car bomb exploded near a military convoy carrying an Iraqi general, killing four civilians and wounding at least seven soldiers.

Iraqi police said the attack was an assassination attempt on Maj. Gen. Rashid Feleih, commander of a special task force, who was not injured. Feleih was apparently on his way to a news conference to talk about the role of the task force, according to police and media reports.

The violence came as American forces prepare for a major offensive against Fallujah and other Sunni militant strongholds north and west of Baghdad in hopes of curbing the insurgency so that national elections can be held in January.

U.S. forces have pounded insurgent positions around Fallujah (search) almost daily, but American officials say the go-ahead for an all-out assault must come from Allawi, the interim prime minister.

However, new pressure mounted Tuesday on Allawi, a Shiite Muslim, to forego an assault and to continue negotiating with the hardline Sunni clerics who run the city, which has become a symbol of Iraqi resistance throughout the Arab world.

Mohammed Bashar al-Faidhi, spokesman of the Association of Muslim Scholars, said his clerical group would use "mosques, the media and professional associations" to proclaim a civil disobedience campaign and a boycott of the January elections.

"In the case of an incursion in Fallujah, there will be a call to boycott elections," al-Faidhi said. "In case of an incursion, more deterrent steps will be taken."

He said that a boycott call by the influential clerical group "will have a great resonance among the people of Iraq."

Such a call by Iraqi Sunnis would probably draw little support among the Shiite majority, believed to comprise about 60 percent of Iraq's nearly 26 million people. The country's leading Shiite cleric, Grand Ayatollah Ali al-Sistani, has been demanding elections for more than a year, and some Shiite preachers have been telling their followers that failing to vote would be sinful.

However, a boycott call could have resonance among central Iraq's Sunnis, who form the core of the insurgency, and inflame passions between the country's major religious communities. Interim President Ghazi al-Yawer, a Sunni, has also spoken out against an attack.

"It's not reasonable to call for elections that are supposed to be democratic and yet a peaceful city gets attacked by weapons, missiles, planes and bombs," said Nabil Mohammed, a professor at Baghdad University's Center for International Studies. He said an all-out attack would "elicit a very big response and support from Iraqis."

U.S. officials believe Fallujah is the stronghold of an Al Qaeda faction led by Jordanian militant Abu Musab al-Zarqawi, whose followers are responsible for numerous car bombings and beheadings of foreign captives.

Al-Zarqawi's group claimed in a Web posting Tuesday that it beheaded Japanese backpacker Shosei Koda after Tokyo refused to withdraw troops from Iraq. The claim was accompanied by a gruesome video showing the young Japanese, whose body was found Saturday in Baghdad, being beheaded on an American flag.

No group has claimed responsibility for the attack in Baghdad in which an American, a Filipino and a Nepalese were taken hostage.

Twelve Americans have been kidnapped or are missing in Iraq. At least three of them have been killed — all beheaded by al-Zarqawi's group.