SEOUL, South Korea (AP) _ South Korean soldiers shot and killed three North Koreans on Thursday, one day after a group of communist infiltrators abandoned their damaged submarine on the rocky coast.

The Defense Ministry said the infiltrators were killed during a shootout. Officials said four communist commandos opened fire after South Korean troops spotted them in a deep mountain valley. Searchers returned fire, killing three. The fourth man fled.

Revising its earlier report, the ministry said a man captured during the shootout turned out to be a South Korean civilian who happened to be in the area, but did not belong to the North Korean group. He was released.

Of the 20 North Koreans believed to have been aboard the submarine, found early Wednesday on a reef off Kangnung, 90 miles northeast of Seoul, one has been captured and 14 now are dead.

An intruder was captured near a remote village Wednesday. Eleven others were found dead in a small clearing on a thickly wooded mountain miles away from the submarine. All had been shot in the head.

Ministry officials said it appeared that 10 of the North Koreans were shot by their leader, who then turned his pistol on himself in an apparent suicide pact to avoid being captured by their capitalist enemies.

Thousands of soldiers and police continued to search Thursday for the remaining infiltrators.

The North Korean captive _ identified as Li Gwang Su, 31 _ told investigators that his submarine lost engine power shortly after leaving its home port of Wonsan on Monday and drifted into South Korean waters.

Investigators said Li refused to disclose where the submarine was headed and what its mission was.

But Gen. Shin Sang-kil said Thursday that interrogators had plied Li with alcohol _ and that now, he was slowly beginning to talk.

``He at first refused to answer, saying he feared for the lives of his family he left in the North, but after drinking four bottles of soju (Korean whiskey), he began to open his mouth,'' Shin said.

Quoting Li, the general said that seven of the 20 men aboard the sub were crewmen and the remaining 13 were trained spies.

Overnight, there were three exchanges of gunfire between fleeing infiltrators and South Korean troops. No South Koreans were injured, the general said. He said local residents reported 12 sightings of suspected intruders during the night.

Defense Minister Lee Yang-ho said in a report to President Kim Young-sam that military operations were directed at blocking an apparent attempt by the infiltrators to flee back home across the border, about 60 miles to the north.

``It is possible that they are trying to escape to the North through mountains and along the coast,'' he said.

Military officials said the North Koreans are specially trained in guerrilla warfare and can cover 32 miles a day through rugged mountains.

During a breakfast meeting Thursday, President Kim told his aides that the infiltration was ``not a case of simple spy maneuvers, but an act of provocation.''

``This infiltration is once again enlightening our people and all people around the world to the true picture of North Korea,'' he said.

The incident appeared sure to further strain Seoul's relations with North Korea, always icy and tense. The two Koreas never signed a peace treaty after the Korean War ended in 1953, and their border remains the most heavily guarded in the world. Nearly 2 million troops are deployed on both sides.

Incursions by North Korea are not new, the latest reported in 1995. In that incident, one communist intruder was shot dead and another captured. Three South Korean policemen were also killed.

The Defense Ministry said the submarine is 112 feet long and weighs 325 tons. It was described as a Sang-o class ship, made in North Korea from a Yugoslav design.