Soviet Foreign Minister Andrei Gromyko warned today that any future violations of "sacred" Soviet borders, such as the South Korean airliner's intrusion into Soviet airspace last week, would receive the "full brunt" of Kremlin retaliation.

Gromyko spoke to the closing session of the European Security Conference in a bitter, unyielding tone that clearly threatened a military confrontation in the skies with the United States. He described the South Korean flight as an American-instigated "criminal act" and said the Soviet response--shooting down the Boeing 747, with 269 people aboard--was, therefore, "in full conformity with the law of the U.S.S.R."

"Soviet territory, the borders of the Soviet Union, are sacred," he declared. "No matter who resorts to provocations of that kind, he should know that he will bear the full brunt of responsibility for it."

As soon as Gromyko finished, Secretary of State George P. Shultz responded, telling reporters that the "implication is that if anyone strays over them, they're ready to shoot them down again." That, he said, shows that for the Soviets, security overrides "human values."

The Gromyko speech and Shultz's reply suggested that Thursday's meeting between the two will be one of the toughest top-level Soviet-American encounters in many years. Shultz has said he will demand that the Soviets account fully for what happened to the South Korean plane, and Gromyko's remarks today leave no doubt that the Kremlin strategy is to blame the whole affair on the United States.

As expected, talk of the airliner's destruction and what to do about it has overshadowed everything else at the ceremonial gathering of officials from 35 countries to endorse a charter for improved East-West relations.

Shultz met this morning with NATO representatives to discuss whether sanctions should be applied to the Soviets. Afterward, British Foreign Secretary Sir Geoffrey Howe said it was agreed at the meeting to "take action as united, as effective and swiftly as possible."

However, what form the governmental action should take is still far from decided. West German officials said they are opposed to suspending flights from the Soviet Union, as Canada has done.

But Britain and several other countries appeared ready to support a short ban on flights by their own national airlines to Moscow--a move which, they say, is technically easier than the other. Except for flights bringing in supplies to Soviet diplomatic missions, the Soviet airline Aeroflot has been barred from the United States since January 1982, in retaliation for the Soviet role in the military crackdown in Poland.

While the consultations continue, allied officials noted that airline pilots in some countries are planning a ban on flights to the Soviet Union. This, they say, will enable governments to get around long-standing aviation agreements with the Soviets by asserting that flights there were prevented by "strike action."

The apparent difficulties in reaching a consensus NATO position on means to rebuke the Soviets could yet dilute the impact of what appears to be genuine agreement that the Soviets have committed a terrible wrong.

"The shooting down of a civilian airliner cannot be justified in any way," West German Foreign Minister Hans-Dietrich Genscher told the conference, in language that was repeated from the rostrum time and time again by Western spokesmen. "We condemn this act of brutality," Genscher said. He demanded that those responsible be punished.

Gromyko's speech was devoted largely to standard Soviet formulations on arms control, human rights and other subjects covered in the three-year Madrid meeting. As he exceeded the 20 minutes allowed for foreign ministers' remarks, it appeared that he might ignore the airliner incident.

Then, abruptly, in remarks that were the first by a top Soviet official since the Korean Air Lines Boeing 747 was shot down last week over Sakhalin Island and the Sea of Japan, Gromyko summarized previous Soviet statements and added flourishes of his own in nine harshly worded paragraphs.

The incident, he said, "is being deliberately exploited" by the United States, which, he said, has "unleashed a wave of slander and shameless insinuations" against the Soviets.

"We resolutely and with indignation reject all this," he continued. "The basic question is this: has anyone the right to violate with impunity foreign frontiers or the sovereignty of another state? No, nobody has such a right."

He repeated assertions that the Korean Air Lines plane was on a U.S.-sponsored intelligence mission and attempted to evade Soviet aircraft once it was spotted.

"That criminal act," he said, "will not be justified either by a dishonest juggling with facts or else false versions dressed in the toga of concern for human rights." This was a reference to American charges that the Soviet action against the plane showed lack of concern for human lives. Gromyko did repeat Moscow's previously expressed "regret" over the 269 deaths.

In his reply, Shultz accused the Soviets of "continuous falsehoods" and said "juggling of the facts is too mild a word for the way the Soviet Union has responded" to the shooting.

Later, Gromyko met for 45 minutes with Britain's Howe. British officials said that Gromyko was as grim in private as he had been in public.

Shultz will meet with Gromyko in the residence of the American ambassador for a meeting of unspecified length. Plans for a luncheon were canceled after the airliner was shot down.