South Korea made no official response today to Soviet charges that the airliner reportedly shot down by a Soviet fighter plane Thursday may have carried photo espionage equipment but South Korean sources who asked not to be identified emphatically denied the allegation.

"I am one hundred percent sure that it is not true," said one South Korean source. He asked a reporter rhetorically: "Do you think such a thing even deserves an answer?"

A statement by Tass, the official Soviet news agency, had charged that the Korean Air Lines Boeing 747 passenger jet may have been engaged in espionage when it flew into Soviet air space over Sakhalin Island north of Japan early Thursday before disappearing with the apparent loss of all 269 people aboard.

"The intrusion into the air space by the mentioned plane cannot be regarded in any other way than a preplanned act," the Soviet statement said. "It was obviously thought possible to attain special intelligence aims without hindrance using civilian planes as a cover."

According to the United States, the airliner was shot down after it had been tracked for 2 1/2 hours on Soviet radar as it veered far off course over the Soviet Union's Kamchatka Peninsula and Sakhalin on its way from New York to Seoul.

Search efforts continued today by Japanese patrol boats, hampered by rain and poor visibility as well as Soviet refusal to permit them to enter Soviet waters in the Sea of Japan, but no evidence of the downed plane was positively identified.

In Tokyo, Soviet Ambassador Vladimir Pavlov reportedly told the Japanese Foreign Ministry that Soviet ships have found debris from an airplane but he did not say whether the wreckage had been identified as that of the Korean airliner.

Pavlov, according to Foreign Ministry officials, said the Soviets were making every effort to find the plane and he expressed regret at the deaths, but he accused Japan of carrying out an anti-Soviet campaign in its charges that Soviet planes downed the airliner.

Japanese officials said tests of oil from a 330-foot-long slick found in the area Friday indicated that the slick had no connection with the downed airliner, The Associated Press reported from Tokyo.

Thousands of demonstrators here and in other South Korean cities protested the apparent shooting down of the airliner today.

Sources here and in Tokyo were unable to throw any new light on the question of why the jumbo jet had strayed more than 300 miles off course for more than two hours or why it was not warned of its misrouting by agencies in Japan that monitored its path.

A spokesman for Korean Air Lines here today said, "We are still investigating and are unable to make any comment now."

Other sources here said they had not been able to turn up any evidence that the plane had been warned by anyone--Soviet, Japanese or American--that it was far off course.

In Tokyo, a Foreign Ministry source said the monitoring of the plane's flight path had been by military intelligence, which had no means of direct voice contact with its pilots. Furthermore, the source said, the military monitors probably would have been unaware exactly what type of craft they were tracking on their radar screens.

"We think that only after it was all over did the Japanese military realize it was a Korean Air Lines flight," the ministry source said.

Japanese sources also said they considered it unlikely that a commercial airliner would have been carrying photo espionage equipment. "The risk would have been too high," said a Foreign Ministry official.

Sakhalin Island is heavily fortified with Soviet air, sea and naval bases and Soviet authorities traditionally have been extremely sensitive about any overflights.

South Korean sources said the last known communication from the jet had come about 3:23 a.m. Thursday, just a few minutes before the Soviet missile was allegedly fired. It gave the plane's position as southeast of Hokkaido, the northernmost of the main islands of Japan, and far from Sakhalin. But according to military monitors, the plane was over Sakhalin or just off its coast at that time.