A car bomb exploded at an airport checkpoint, a Lebanese American was reported kidnapped from his home, three headless bodies were found under a bridge and a U.S. soldier was killed by a roadside bomb as violence continued in and around the Iraqi capital Wednesday.

Hungary, meanwhile, announced that it would withdraw its 300 troops from the country by the end of March, after Iraqi elections planned for January.

"It is an obligation to stay until the end of the election, while staying much longer is impossible," the Hungarian prime minister, Ferenc Gyurcsany, told reporters in Budapest, the capital. "From then on, the existence of a stable, secure and democratic Iraq must be ensured by other, mainly political means."

Hungary, a member of NATO since 1999, is among 29 countries participating in the U.S.-led military occupation, almost all of which maintain only small forces in Iraq. The Hungarians have carried out aid operations from their base in Hilla, a usually quiet city south of Baghdad.

Bulgaria, another coalition member, announced that it would trim its force of 483 soldiers by 10 percent next month after moving from Karbala, about 60 miles southwest of Baghdad, to Diwaniyah, also south of the capital.

The car bomb detonated at a checkpoint leading to Baghdad's heavily fortified international airport. When a guard approached an SUV and asked the driver to produce identification, the man at the wheel shouted, "Allahu Akbar!" -- or "God is Great!" -- and the vehicle exploded, said Mais Naib, 38, one of several Iraqi Airways employees waiting at the checkpoint.

"There were no Americans nearby," she said. "We are in real danger. I do not know what to do. Shall I sit home and stop coming to work? That is exactly what they want us to do -- they do not want to see Iraq raise up again. I do not know what to do."

Reports of casualties varied. The Reuters news agency, citing witnesses and hospital staff members, said an Iraqi security guard was killed and seven civilians were injured.

A member of the Army's 1st Infantry Division was killed and another soldier was injured when a roadside bomb exploded beside their combat patrol about 10 miles southeast of the capital near Salman Pak. The dead soldier was not identified because his next of kin had not been notified.

The kidnapped Lebanese American was identified by the Associated Press as Radim Sadeq, an employee of a cell phone company. He was abducted after answering the front door to his house in Baghdad's Mansour district, the same prosperous neighborhood where an unidentified U.S. citizen and four other people were kidnapped two days earlier, and where two Americans and a Briton were abducted last month. Those three were later beheaded.

Also Wednesday, three beheadings were shown on a tape received by the Arab satellite news channel al-Jazeera. A group calling itself the Brigades of the Iraqi Honorables asserted responsibility for killing the three men, who were identified as members of the Iraqi National Guard. Three bodies believed to be theirs were found under the 14th of July Bridge, an emblem of the U.S. presence in Iraq because it is reserved for travelers cleared to cross the Tigris River into the fortified Green Zone, which is guarded by U.S. forces.

A fourth decapitation was posted on a Web site by the Ansar al-Sunna Army, a group that has boasted of several beheadings. In a statement, the group identified the victim as Maj. Hussein Shanoun, an officer in the nascent Iraqi army being trained by U.S. forces.

Four Jordanian truck drivers were reported kidnapped Wednesday, a government spokeswoman said from Amman, the Jordanian capital, according to the Associated Press.

More than 170 foreigners have been kidnapped in Iraq since insurgent attacks intensified in April, the one-year anniversary of the fall of Baghdad. At least 30 of the victims were subsequently killed.

Iraqi and U.S. officials have said they expect abductions and other attacks across Iraq to rise further if U.S. forces lead an offensive against Fallujah, a city 35 miles west of Baghdad that local and foreign fighters have controlled since April.

British Prime Minister Tony Blair on Wednesday urged insurgents to lay down their weapons and negotiate the peaceful return of the city to Iraq's interim government. But Marine, Army and Iraqi forces continued preparations for a major assault, and U.S. warplanes bombed what a military statement said was an insurgent command post in the city.

Special correspondent Naseer Nouri contributed to this report.

A U.S. soldier surveys a damaged vehicle at the scene of a car bomb attack near a checkpoint on the highway to the heavily fortified Baghdad airport.A joint U.S.-Iraqi military convoy returns from a search operation in Baghdad's Sadr City neighborhood.