A South Korean soldier was killed and a U.S. soldier wounded today at the truce village of Panmunjom in a shoot-out with North Koreans who apparently were trying to stop one or two Soviet citizens from defecting.

Three North Koreans were reported killed in the incident at the neutral site, located in the Demilitarized Zone that divides the Korean Peninsula.

According to television reports, one Soviet citizen safely reached the South during the incident. He reportedly was flown by helicopter to Seoul, where he requested asylum in the United States.

In a broadcast tonight, North Korea's state radio said the incident began when a foreign tourist inadvertently stepped across the demarcation line and was seized by American guards. The radio said the United States should take responsibility for the "barbaric act" and return the man.

The tone of the North Korean broadcast seemed to indicate that Pyongyang was not going to halt discussions with the South about improving relations.

Under the armistice agreement, both sides are allowed to maintain armed guards at Panmunjom, where periodic talks have taken place for the past three decades. South Korean and U.S. military personnel jointly guard the South's side.

Both sides bring tourists to Panmunjom, in the company of guides whose narratives are heavily political. North Korean soldiers frequently are seen posing for pictures at the demarcation line with South Korean guards a few feet behind them.

Television reports said the incident began when a Soviet citizen guiding a group of Soviet tourists around the North Korean area stepped across the demarcation line just before noon today.

According to the U.N. Command, 20 to 30 North Korean guards then crossed into the South's territory and opened fire in an attempt to stop the defection.

South Korean soldiers fired in self-defense, a command spokesman said.

The South Korean casualties were not identified, pending notification of relatives. In Washington, the Pentagon identified the wounded American as Pvt. Michael Burgoyne, 20, of Portland, Mich., The Associated Press reported.

On Saturday, a U.S. Embassy official in Seoul identified the Soviet as Vasily Yakovlovich Matuzok and said he was "alive and well." The state-run (South) Korean Broadcasting System said he was a "Russian tourist guide," and Japanese reports put his age at 22.

Deputy White House press secretary Marlin Fitzwater said the Soviet defector was in the U.S. Embassy in Seoul, "and his situation is being discussed with embassy officials."

Fitzwater, speaking in Santa Barbara, Calif., where President Reagan is vacationing, said he had no further details but added, "We regret the loss of life in this difficult part of the world."

[Burgoyne's father, George, said in Portland that his son's "prognosis is good, he's ambulatory, his life is not in danger. He was shot in the jaw. . . . He's being fed (intravenously), but his condition appears to be fair."]

According to television reports, the successful defector told South Korean authorities that a second Soviet citizen had tried to defect with him but was wounded and captured.

It was unclear what effect the incident would have on a newly opened dialogue between North and South Korea aimed at establishing trade and reuniting families separated by the Korean War. The next talks are scheduled for Dec. 5.

Some analysts in Seoul predicted little effect because the incident appeared to have been accidental. However, others expressed fear that it would poison the current mood of cautious trust and cooperation between the two sides.

"The shooting incident was accidental, and I don't believe it will have any negative effect on the Seoul-Pyongyang economic talks and the Red Cross conference," a senior official in the South Korean Foreign Ministry said.

The United Nations Command condemned today's incident as a violation of the armistice agreement that ended the Korean War in 1953 and called for a meeting with North Korean security officers to preclude further trouble.

It was the most serious incident in the Demilitarized Zone since June 1983, when the South Korean Army reported killing three North Korean infiltrators.

In 1981 a Czech Army private defected at Panmunjom without incident. He was assigned to the Neutral Nations Supervisory Commission, a four-nation body that oversees the armistice agreement.

Panmunjom was the scene of violence in August 1976, when North Koreans used ax handles to fatally club two U.S. Army officers who were leading a party of workers on a tree-trimming expedition.