Soviet destruction of a civilian South Korean jetliner has cast a pall over US relations with the Soviet Union and could harden attitudes toward Moscow around the world.
In a news conference Thursday, Secretary of State George Shultz said that a Soviet MIG fighter plane shot down the Korean Air Lines 747 jumbo jet over Soviet territory near Sakhalin Island. There were 269 people aboard, including US Rep. Lawrence McDonald (D) of Georgia. There were no known survivors.
''We can see no excuse whatsoever for this appalling act,'' Mr. Shultz said. He noted that the Soviet charge d'affaires in Washington was called in to hear an American statement of ''strong concern'' and a demand for an explanation from the Soviet Union. President Reagan was described as deeply disturbed and concerned.
The secretary of state said the Soviet attack - which occurred early Thursday local Asian time, or 2:26 p.m. Wednesday EDT - came after Soviet MIGs had tracked the commercial plane for 21/2 hours and had made visual contact with it. Some defense experts said the attack immediately raised questions as to how well controlled the Soviet armed forces are. The Soviets are normally thought to operate under rigid control.
The seriousness of the incident will almost certainly lead to some countermeasures from both the US and Japan, and to a further cooling of relations between those two nations and Moscow. Korean Air Lines officials said 72 Koreans, 22 Japanese, 34 Chinese from Taiwan and Hong Kong, and 112 others, including a number of Americans, were aboard the plane besides the crew.
In Japan, the incident could contribute to pressures for increased defense spending and greater military preparedness.
The attack came at a time when US relations with the Soviet Union were improving slightly and at a time when a US-Soviet summit meeting was viewed as a possibility for next year. The Soviets had recently shown greater flexibility, at least on secondary issues, in the strategic arms reduction talks (START) in Geneva.
But State Department officials argue that the picture was a decidedly mixed one, because, in their view, the Soviets have ''not been helpful'' to the US in regional conflicts - most notably those occurring in the Middle East, Central America, and southern Africa. Following the shooting down of the South Korean jetliner, Soviet behavior is likely to become the subject of much sharper scrutiny.
With Soviet President Yuri Andropov wooing West European public opinion and trying to put out peace feelers on other fronts, it is difficult to imagine how the destruction of an unarmed jetliner over Soviet territory would benefit the Soviet Union.
Former Secretary of State Alexander M. Haig Jr., summed up feeling in official circles in Washington when he said on Thursday that the incident ''would tend to sharpen people's concern about the whole area of arms control, mutual restraint, and the existing management of the Soviet system itself.''
The command and control of Soviet forces ''is a key question to be reviewed by everyone in the period ahead,'' said Haig.
Geoffrey Murray reports from Tokyo:
The South Korean airliner blundered into an extremely sensitive area where a Soviet hair-triggered reaction generally prevails, Japanese defense experts said Thursday.
Soviet fighters from bases on the island of Sakhalin and nearby islands have scrambled on a number of occasions in recent years when a civilian plane strayed too close.
According to a knowledgeable source: ''The Russian pilots react quickly and they are ordered to deal with intrusions severely.''
The South Korean government, describing the attack as an inhumane act, said countermeasures were being studied without specifying what these might be. Seoul does not have diplomatic relations with Moscow and is relying on Japan and the US to press for the truth.
The Korean pilot of the Boeing 747 had a choice of three designated lanes, the closest within 18.6 miles of Soviet territory. The latter route across the Japanese island of Hokkaido was apparently chosen, but for unexplained reasons the aircraft was traveling well to the north across the southern tip of Sakhalin. A radio report from the pilot indicated he believed he was on course, however.
Japanese radar showed three blips tentatively identified as Soviet MIG-23s rising in challenge. The airliner made a final attempt to contact a Japanese radar station but static made it impossible.
Aviation expert Kunio Yanagina commented: ''The sudden disappearance from radar is very strange, as you would normally expect to track a plane even if it was falling to the earth. The only explanation would seem to be a very sudden explosion.''
It seems to have been the Korean airliner's misfortune to stray into an area of extreme Soviet military sensitivity. Sakhalin and nearby islands, seized from Japan at the end of World War II, have been turned into major bases. Japanese defense sources estimate there are two Army divisions on Sakahlin and more than 100 jet fighters.
The fighter buildup is regarded as a counter to the American military presence in Japan, especially the planned 1985 deployment of F-16s at a northern base within striking distance of vital Soviet sea lanes.
The bases on Sakahlin and the other islands could provide protection for Soviet submarines operating in the Sea of Okhotsk, which would launch nuclear attacks on the US and its allies should war break out.