Kidnappers beheaded a South Korean civilian who had been held captive since last week after the government in Seoul rejected a demand that its troops be withdrawn from the international military force in Iraq, South Korean officials said Wednesday.

U.S. soldiers found the body of Kim Sun Il, 33, at 5:20 p.m. Tuesday on the side of a road between Baghdad and Fallujah, the city west of Iraq's capital where Kim was abducted last Thursday. The South Korean Embassy in Baghdad confirmed that the body was Kim's.

Army Brig. Gen. Mark Kimmitt, the chief U.S. military spokesman in Iraq, said in a statement: "It appears that the body had been thrown from a vehicle. The man had been beheaded, and the head was recovered with the body."

Kim's captors, a group that identified itself as Jamaat al-Tawhid and Jihad, had threatened in a videotape released late Sunday to kill him unless South Korea agreed to withdraw the 660 troops it has in Iraq and cancel a planned deployment of 3,000 additional forces to northern Iraq.

In the video, Kim was shown pleading for his life. "I don't want to die. I don't want to die," Kim screamed. Pleading for South Korean soldiers to leave Iraq, he said: "I know that your life is important, but my life is important."

The South Korean government rejected the demand Monday and attempted to negotiate for Kim's release. On Tuesday, in another videotape broadcast by al-Jazeera, the Arabic satellite television network, the same group said it had beheaded Kim.

The group, headed by Abu Musab Zarqawi, a Jordanian linked by U.S. officials to al Qaeda, also asserted responsibility for the beheading last month of an American businessman, Nicholas Berg. In Saudi Arabia, a group claiming affiliation with al Qaeda said it was behind the beheading of another American, Paul M. Johnson Jr., whose decapitated corpse was found Friday on the outskirts of Riyadh, the Saudi capital.

Kim, an evangelical Christian who had studied Arabic, English and theology, was working as a translator for a South Korean contractor that provided supplies to the U.S. military in Iraq. His family said he was hoping to save enough money to fulfill his dream of becoming a missionary in the Middle East.

President Bush on Tuesday condemned the beheading as "barbaric" and said he remained confident that South Korea would go ahead with plans to send troops to Iraq. "The free world cannot be intimidated by the brutal actions of these barbaric people," Bush said.

In Seoul, the semi-official Yonhap news agency said President Roh Moo Hyun was told of Kim's slaying at about 1 a.m. Wednesday. Roh appeared stunned by the news, according to the news agency, having received an upbeat briefing on the prospects for Kim's release a few hours earlier by Vice Foreign Minister Choi Young Jin.

In brief, nationally televised remarks later Wednesday, Roh said he felt "heartbroken" over the killing but added: "We shouldn't let them achieve what they want through terrorism. We strongly denounce such an act of terror and are firmly determined to cope with it in conjunction with the international community," according to the Reuters news agency.

The death "breaks our heart," Shin Bong Kil, a South Korean Foreign Ministry spokesman, said in announcing Kim's death.

In the video broadcast on al-Jazeera on Tuesday, five hooded men -- two armed with guns and another with a sword -- surrounded a kneeling man, believed to be Kim. He was dressed in an orange jumpsuit similar to those worn by prisoners and blindfolded with a strip of cloth. The broadcast did not show the beheading, but a spokesman for al-Jazeera said a subsequent unaired portion of the tape showed one of the men cutting off Kim's head with a knife, Reuters reported.

On the video, one of Kim's captors delivered a message to the South Korean people, saying: "Stop lying. Stop deceiving, because your army is not here for the Iraqis. It is for the Americans."

In a news briefing early Wednesday, Shin told reporters that "our government's basic spirit and position has not changed. We confirm that again, because our troop deployment is for reconstruction and humanitarian aid support for Iraq."

But Kim's death appeared almost certain to broaden opposition in South Korea to the country's already unpopular involvement in Iraq. Public opinion polls show that more than 56 percent of the population opposes the troop deployment. More than a thousand South Koreans took to the streets for a second day on Tuesday, demanding a withdrawal from Iraq, while hundreds more took part in candlelight vigils for Kim.

Most South Koreans were asleep when Kim's death was reported at about 1:30 a.m. Wednesday. Television networks quickly turned their attention to the lower-middle-class home in Pusan, South Korea's second-largest city, where Kim's parents collapsed in grief and tears, lying prostrate before a traditional death altar they had arranged with his photo.

"How could it have come to this?" a tearful neighbor shouted at reporters as she consoled Kim's parents. "How can we have faith in the world anymore?"

A distraught college friend of Kim's demanded that the government explain why it failed to do more to win his release.

"We longed for his safe return with the candlelight vigils, and people were desperately praying, all in vain," said Lee Sang Hoon, 27. "I just can't believe this has happened. Somebody has got to take responsibility for this."

In Iraq, where the U.S.-led occupation is scheduled to hand over political authority to an interim Iraqi government at the end of the month, the beheading of Kim again brought home the deadly nature of a months-long campaign by insurgents to kidnap foreigners.

In addition, foreigners and Iraqis have been targets of almost daily bombings and assassinations in recent weeks, which continued Tuesday in the northern city of Mosul with the killings of the dean of the college of law at Mosul University and her husband. Layla Abdulla Saeed and Moneer Yahya Ali Khairo were found dead outside their home, the U.S. military said.

Meanwhile, a U.S. military judge refused to grant a new preliminary hearing for a soldier accused of abusing detainees at the U.S.-run Abu Ghraib prison west of Baghdad but said he would allow defense attorneys to interview the top U.S. military commanders in Iraq about the scandal as the soldier's trial moved forward.

The rulings in the case against Staff Sgt. Ivan L. "Chip" Frederick II were identical to the ones the judge, Col. James Pohl, made the day before in pretrial proceedings for two other soldiers charged with abuse.

Seven soldiers from the 372nd Military Police Company, based in Cresaptown, Md., have been charged with beating and humiliating detainees in U.S. custody at the prison.

Pohl had rescheduled Frederick's pretrial hearing for the end of next month after his civilian defense attorney failed to appear in court in Baghdad on Monday. But Frederick waived his right to have his civilian attorney present, and the judge took up the matter on Tuesday with Frederick and his military attorney, Capt. Robert Shuck.

Faiola reported from Seoul. Special correspondents Johee Cho in Seoul and Huda Ahmed Lazim in Baghdad contributed to this report.

The parents of Kim Sun Il, a South Korean contractor kidnapped Thursday in Fallujah, Iraq, react to news of their son's fate. An image aired on the al-Jazeera television network appears to show Kim with his captors. An al-Jazeera spokesman said an unaired portion of the video showed Kim's beheading.