The government would do its best to seek the release of 33-year-old businessman Kim Sun-il, who has been shown repeatedly on South Korean television pleading for his life, Vice Foreign Minister Choi Young-jin told reporters.
Choi said Kim, an Arabic graduate, had been seized in Falluja on 17 June - the day before South Korea announced where its troops would be deployed after months of agonising because of security concerns and public opposition.
In addition to Kim, the group is holding about 10 other foreigners as well, the businessman's company president told the Yonhap news agency on Monday.
Kim Chun-ho, president of Gana General Trading, told Yonhap from Iraq an employee sent to Falluja to negotiate with the captors, had seen about 10 foreigners including at least one European journalist and some people from the KBR engineering and construction unit of US firm Halliburton.
The group holding Kim said South Korea had 24 hours from Sunday night to withdraw its decision or they would kill him, Aljazeera satellite channel reported.
"It's very regrettable and unfortunate," said Roh in comments released by the presidential Blue House. "I request the foreign ministry and other related agencies to make all their efforts to save him and address the issue with great care and urgency as Koreans are very concerned about the incident."
Roh insisted South Korean troops were being sent to rebuild Iraq, not to "engage in hostile activity" against Iraqi people or Arabs.
The president of Kim's company, which supplies goods to the US military commissary, had initially sought to negotiate with the captors without telling the government, Choi said.
"I am telling you that there will be no change to our government's basic spirit and position - our plan to send troops to Iraq is for the support and reconstruction of Iraq," Choi said. He chairs a special task force set up to handle the crisis. The ministry called in Arab ambassadors to ask for help.
Aljazeera broadcast the videotape showing masked men standing behind Kim as they made their threat. South Korean television stations showed the film repeatedly.
The captive has pleaded for his
life to be saved
YTN television quoted Kim's family as saying he had called, sobbing, from Iraq. He is the seventh of eight children.
Kim worked for Gana General Trading, a company with 12 employees in Iraq, Yonhap news agency said.
Many South Koreans reacted with shock, particularly because of the footage of Kim imploring people to help to free him. But most said Seoul should not alter its decision to send troops.
"I felt terribly chilled this morning watching the Korean crying and yelling in front of the terrorists' camera. I am so sorry for his family. But feeling sorry and national security should be considered separately," said Sung Jeong-hun, a 29-year-old graduate school student in Seoul.
Ryu Hee-man, a 51-year-old businessman, said he had expected an incident of some kind so he was not greatly surprised. Others said they had been shocked.
"It's sad and may trigger a further delay in the troop deployment or an early withdrawal of South Korean soldiers in Iraq," said Kim Byung-ho, a 34-year-old engineer. "But I don't think the government should change its commitment."
Roh is unlikely to change tack, despite protests against the plan, although the crisis could magnify public and parliamentary opposition.
"I request the foreign ministry and other related agencies to make all their efforts to save him and address the issue with great care and urgency as Koreans are very concerned about the incident"
South Korean president
He views the deployment as a tough but crucial gesture to support Seoul's main ally, the United States, which has 37,500 troops stationed in the South to deter North Korea.
Friday's announcement capped months of debate in South Korea on a pledge first made to US President George Bush by Roh in October last year and approved by parliament in February.
South Korea already has about 670 military engineers and medics in southern Iraq, and they will join the larger deployment in the North. About half the troops are combat-ready forces trained to protect the non-combat troops.