Updated

South Koreans poured out sorrow and anger Wednesday over the beheading of a countryman in Iraq, while President Roh Moo-hyun (search) vowed to "deal sternly" with terrorism and push ahead with a large troop expansion.

The nation awoke to banner headlines that militants had killed 33-year-old Kim Sun-il (search) on Tuesday after Seoul refused to meet his kidnappers' demand of ceasing involvement in Iraq.

The execution renewed debate over South Korea's contribution to the U.S.-led coalition in Iraq and Roh's plan to send 3,000 more troops starting in August. When complete, the deployment will make South Korea the largest coalition partner after the United States and Britain.

Authorities heightened security at government buildings and the U.S. Embassy in case of protests over Kim's death or Roh's decision.

"The government was irresponsible and didn't do enough to save him," said Park Bong-ju, a 28-year-old office worker. "This tragedy happened because of the government's plan to send troops. We must cancel a dispatch plan and withdraw soldiers who are already in Iraq."

About 2,000 protesters gathered at a candlelight vigil Wednesday night to mourn Kim's death and oppose the troop dispatch. Many held placards reading "Bush and Roh killed Kim Sun-il" and "We don't want to die. Korean troops get out." Scores of riot police stood by.

However, South Korea's largest newspaper, Chosun Ilbo, offered support for the troop expansion.

"This incident was shocking and tragic, but it mustn't shake our decision and principle to send troops to Iraq," the newspaper said in an editorial. It added that increased criticism over the deployment will only be "fulfilling perfectly the intention of the terrorists."

Kim's plight had gripped the country since Sunday, when he was shown on a video released by his captors screaming "I don't want to die" and urging the government to leave Iraq.

Kim was a devout Christian who once considered missionary work in the Arab world, South Korean media have reported. His body was found by the U.S. military west of Baghdad on Tuesday night.

South Korea quickly reaffirmed its commitment to the troop dispatch after Kim's death, and Roh tried to assure both his country and the Iraqis that South Korean soldiers would help rebuild Iraq, not fight its people. About 600 South Korean military medics and engineers are already in the southern city of Nasiriyah.

In a televised address Wednesday morning, Roh called the slaying a crime against humanity. He condemned terrorism, vowing "to deal sternly with it together with the international community."

"When we think of his desperate appeals for life, our hearts are wrenched with grief," Roh said.

Some South Koreans supported Roh's decision not to back down.

"This is time for the nation to tighten its unity and show to the world we stand together in a difficult time," said Cho Hang-duk, a 42-year-old office worker. "I don't think the government should cancel its troop deployment."

But a group of 50 lawmakers, many from Roh's ruling Uri Party, drew up a resolution urging the government to reconsider.

"It is impossible to implement the task of peace and reconstruction at a time when not only the troops, but also ordinary civilians, are under threat — as witnessed by the killing of Mr. Kim Sun-il," the resolution said.

Civic and student groups called for a cancellation of the deployment and planned protests.

South Korean television showed Kim's distraught family weeping and rocking back and forth with grief at their home in the southeastern port city of Busan.

A banner in the street outside their home was still there, reading, "The South Korean people have never fired a single bullet at Iraqis. Please send back Kim Sun-il alive." South Korea's KBS television said angry residents in his neighborhood later tore down placards that read: "Koreans are friends of the Iraqis."

South Korea said it would redouble its efforts to evacuate its civilians in Iraq to prevent a repeat hostage crisis. Seoul officials believe about 20 South Korean businessmen are currently in Iraq. In April, seven South Korean missionaries there were briefly detained.

The government also banned domestic Internet portals from showing footage of Kim's beheading and warned it would shut down those that don't comply.

A video of the blindfolded Kim kneeling before masked captors before his killing was aired overnight by pan-Arab TV station Al-Jazeera. The network said it decided not to air video of Kim being executed because it was too gruesome.

Images of the recent beheadings by militants of Americans Nicholas Berg (search) in Iraq and Paul M. Johnson Jr. (search) in Saudi Arabia were widely distributed over the Web.