SEOUL - South Korea said Thursday that North Korean soldiers shot dead a South Korean government employee who had gone missing in waters near the inter-Korean border earlier in the week, condemning the alleged act as a brutal killing.

Separately, a military official said that it seems North Korean troops were questioning the government employee before an alleged order came down for him to be shot.

This is the first known killing of a South Korean national by the North since Moon Jae In became president in 2017 and is likely to heighten tensions between the Koreas.

Moon called the execution-like killing "shocking" and said it "cannot be tolerated for any reason," according to a presidential spokesman.

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The Oceans and Fisheries Ministry employee was reported missing Monday while carrying out duties in waters off the western island of Yeonpyeong in the Yellow Sea.

"We have confirmed that North Korea has committed an act of brutality by shooting a South Korean and burning his dead body," the Defense Ministry said in a press briefing.

The ministry said North Korea is solely responsible for the episode, calling for an apology and explanation from the northern neighbor and punishment for those responsible for the man's death.

The ministry said it reached its conclusion after "analyzing several pieces of information collected by our military."

The Oceans and Fisheries Ministry employee had been on patrol for potential illegal fishing in the waters. He disappeared from the boat, leaving his shoes behind, and it is believed he attempted to defect to the North by crossing into the North.

The military official said he drifted in the water with a life vest on and was found and questioned by North Korean troops the following day. After killing him, the troops poured oil on the body and burned it while in the waters, the official added.

It is unclear why North Korea killed the man, but there is speculation that it was part of an effort to stem the spread of the new coronavirus.

Moon's office held a meeting of the National Security Council on Thursday and said it strongly condemns the North Korean action.

An official of the office said the president, after being briefed on the case on Wednesday morning, ordered his top officials to inform the public of details if they were corroborated.