VILNIUS, U.S.S.R., JAN. 12 (SATURDAY) -- Soviet troops supported by tanks and armored cars occupied several buildings and fired live ammunition Friday to quash symbolic resistance by Lithuanian activists, the biggest show of force here since the Baltic republic declared its independence from Moscow.

Lithuanian government officials said that at least seven civilians were injured during a day of confrontation between the Soviet troops and demonstrators who massed around buildings thought to be in danger of an army takeover. The Soviet state-controlled news media painted a grim picture of mounting chaos in Lithuania, alleging that the pro-independence government was losing control of the situation.

The sudden use of force by the Soviet military came less than a day after Soviet President Mikhail Gorbachev appealed to the Lithuanian parliament to restore the validity of the Soviet constitution or face the consequences. Lithuania, one of the three Baltic republics annexed by the Soviet Union in 1940, formally proclaimed the restoration of its prewar independence on March 11 last year.

The small pro-Moscow Lithuanian Communist Party announced Friday night that it was setting up a Committee of National Salvation with the goal of replacing the republic's democratically elected government and saving its 3.4 million people from what it claimed was chaos and anarchy. It refused to make public the membership of the committee, saying that to do so could endanger their safety.

Many Lithuanian politicians expressed fear that Gorbachev could use Friday's clashes as a pretext for declaring direct presidential rule in the republic, suspending its democratic institutions. But others insisted that the day's military actions were merely a continuation of a year-long war of nerves by the Kremlin aimed at scaring the population into submission.

In an interview Friday evening, Lithuanian President Vytautas Landsbergis said he tried to call Gorbachev twice during the day to urge him to instruct the armed forces under his command "to stop the bloodshed," but was told that the Soviet leader was unavailable. Landsbergis compared the day's events to pressure exerted by the Kremlin on Lithuania in June 1940, as a result of which its leaders were forced to accept the republic's incorporation into the Soviet Union.

"This time we are going to behave differently. We have received several ultimatums, but we have not capitulated," Landsbergis said, as thousands of pro-independence Lithuanians sang patriotic hymns in the newly named Independence Square outside the parliament building.

Acknowledging that direct presidential rule from Moscow was now a distinct possibility, Landsbergis said the Kremlin appeared to be timing a crackdown here to coincide with the climax of the crisis in the Persian Gulf.

The parliament hastily reconfirmed most of the government that had resigned on Tuesday in an effort to deny Moscow the opportunity of declaring that Lithuania is without a government.

The immediate result of Friday's army action has been to fire up the nationalist fervor of the Lithuanian majority and to encourage the disgruntled Russian-speaking minority to demand the dissolution of the Lithuanian parliament. Tens of thousands of Lithuanians have responded to appeals to form human shields around government buildings to prevent them from being taken over by the military.

Soviet television news reported Friday night that 23 major factories and federal institutions, including the Lithuanian branch of the state airline Aeroflot, had gone on strike. Russian-speaking workers at the republic's major power plant have declared that they will cut off electricity supplies starting Tuesday unless the parliament agrees to Gorbachev's demands that it recognize the supremacy of the Soviet constitution.

Despite Friday's forcible seizure of buildings in Vilnius and other Lithuanian cities, the Kremlin has so far stopped short of a final confrontation with the rebel republic. At least two of the buildings taken over in the capital had been nationalized recently by the Lithuanian parliament, a point that enables the Soviet army to argue that it acted to protect federal property.

The buildings seized in Vilnius included the headquarters of the Department for National Security, a fledgling national guard, which formerly belonged to a federal veterans' organization, and the republic's largest publishing house, formerly the property of the Communist Party. The army also occupied the control center for the main railroad station, bringing rail traffic to a halt throughout the republic, and a clubhouse that stored weapons for hunters and fishermen.

About 20 tanks and armored personnel carriers roamed the streets of Vilnius early this morning, followed by carloads of Lithuanians. Soldiers took over another National Security Department building, but made no move against the parliament building, where an all-night independence festival was in progress.

Thousands of Lithuanians gathered around the building early today, singing and dancing by the light of street fires and television floodlights. Inside, legislators and National Security activists wandered through darkened corridors. In some offices, volunteers took up positions with hunting rifles. The nonstop presence of television cameras made a takeover attempt unlikely.

Outside the capital, National Security Department offices in several Lithuanian towns were also reported to have been occupied by soldiers, as were Lithuanian customs posts along the border with Byelorussia.

Lithuanian officials said one of those injured Friday, a driver whose truck was crushed by a tank, was in critical condition.

The Lithuanian government estimates that about 95,000 Soviet troops are now stationed in the republic, including several thousand paratroopers recently flown in from the Russian cities of Vitebsk and Pskov. The National Security Department has 2,500 full-time employees, including several hundred youths wanted by the Soviet authorities for draft evasion, and has mobilized tens of thousands of additional volunteers.

Officials in neighboring Latvia said that Soviet Defense Minister Dmitri Yazov and Chief of Staff Gen. Mikhail Moiseyev had assured them in a Moscow meeting Friday that no additional troops would be sent there. No new incidents were reported Friday in either Latvia or Estonia.

As the fledgling Lithuanian militia prepared to defend government buildings from attack by the Soviet army, there was some grumbling that the government had failed to supply its volunteers with adequate weapons. "They waited for 10 months and did not do anything. How can we defend ourselves properly if all we have is sticks?" asked a 25-year-old sculptor on duty at Vilnius's television tower.

Lithuanian leaders are aware that it will be impossible to defend their democratic institutions if Gorbachev decides on a full-fledged crackdown. They are calculating, however, that their tactics of symbolic and largely nonviolent resistance will win the sympathy of the international community, forcing worldwide condemnation of the Kremlin.

The head of the National Security Department, Audrius Butkevicius, discounted suggestions that Friday's show of force by the Soviet army could have taken place without Gorbachev's explicit approval.

"They did not need to use tanks and armored cars to take these buildings. It was all a deliberate attempt to intimidate us and find some pretext for introducing their army," he said.