N. Korea Warns U.S. After Commandos Killed

North Korea warned American military officials Wednesday that “serious consequences” would follow the recent killing of North Korean commandos who had sneaked into South Korea by submarine, American officials said.

Tensions on the Korean Peninsula also rose after the disclosure today of the mysterious slaying of a South Korean diplomat in Russia.

The circumstances surrounding the killing were so strange and suspicions are so deep that there was immediate widespread speculation that the attack was a North Korean assassination, although there was no proof of such involvement.

The South Korean government ordered stepped-up security for its diplomats around the world and sent a team of investigators to Russia.

The North Korean warning came Wednesday in a meeting at the truce village of Panmunjom, near the demarcation line that separates the two Koreas. At the end of the meeting, the senior North Korean official tried to pass a note to the Americans warning that “serious consequences, which would be announced, would occur as a result of the deaths of their soldiers,” the United Nations Command said in a statement.

Officers of the United Nations Command, which consists mainly of American forces, read the note but refused to accept it.

“We take all these kinds of threats seriously, and our guys are always in a high state of vigilance,” Jim Coles , a civilian spokesman for the United States forces in South Korea, said.

President Kim Young Sam of South Korea met with senior military officials and called on them to be especially alert for any action by North Korea.

The North Korean threat follows a bizarre episode in which a 325-ton North Korean submarine ran aground on the South Korean coast on Sept. 18, in an area near a number of South Korean military installations. Some 26 North Koreans slipped ashore, some disguised in South Korean army uniforms and carrying South Korean submachine guns.

A search by 40,000 South Korean troops has led to the capture of one commando, the death of 11 and the discovery of the bodies of 11 others who were apparently killed by their North Korean comrades. Three other infiltrators remain on the loose.

The slaying of the South Korean diplomat, Choi Duk Keun, occurred on Tuesday in the eastern Russian city of Vladivostok. The killing aroused special attention because the Russian police reportedly suggested it was the work of a team of two or more professional assassins.

Choi, who was responsible for monitoring North Korean activities in the area, was carrying a passport and $1,200 in cash when he was attacked, but nothing was taken from him. He was walking up the stairway to his seventh-floor apartment when he apparently was hit on the head and stabbed twice in the stomach with something sharp. His body was found on the stairway.

South Korean officials said that the wounds in the stomach may have been caused by a hypodermic needle rather than a knife.

Russian doctors are conducting an autopsy on Choi, and South Korean television reported that the police are said to be searching for two men who had Asian complexions and were seen in the stairway shortly before the attack by a Russian woman who lived in the building.