VILNIUS, U.S.S.R. (AP) _ Soviet troops seized the Lithuanian national guard headquarters and the republic's main printing plant today, and the Lithuanian government said soldiers fired over a crowd outside the printing plant.

Troops at the printing plant shot one young man in the face, said Aidas Palubinskas, a Lithuanian parliament spokesman. Three other people were shot and three suffered broken bones, said ELTA, the Lithuanian state news agency.

Hundreds of Lithuanian nationalists formed a human ring to try to defend the republic's television tower. The nationalists have been guarding the republic's parliament buildings for two days, fearing an attack by the Red Army or Russian nationalists opposed to Lithuanian independence.

Lithuanian President Vytautas Landsbergis tried to telephone Soviet President Mikhail S. Gorbachev today, but was told Gorbachev was having lunch and would not take the call, parliamentary spokeswoman Rita Dapkus said.

Landsbergis left a message saying Soviet troops were ''spilling blood in the republic of Lithuania, and that (he) must issue an order to halt this action immediately,'' she said.

Gorbachev indicated Thursday he might impose direct presidential rule unless Lithuania complied with the national laws it has flouted since declaring independence on March 11.

Neither the Soviet Constitution nor national laws define what measures could be taken under presidential rule, but they could include disbanding the parliament and banning demonstrations and political groups.

Landsbergis has said imposing presidential rule would be a ''new and dangerous step,'' and appealed for Western support in the standoff.

Some such support came today.

The NATO alliance and the European Community urged the Kremlin to refrain from violence in Lithuania and to seek talks with Baltic leaders. Britain summoned the Soviet charge d'affaires in London to the Foreign Office to protest the Soviet troop actions in Lithuania, and Lithuania's neighbor Poland appealed for a peaceful solution.

In its first report on today's confrontation, the official Tass news agency issued a three-paragraph dispatch saying troops occupied the printing plant so they could return it to the Communist Party. Independence supporters had claimed ownership.

In the clash outside the plant, soldiers used an irritant gas on the crowd. Britain's Independent Television News said one of its cameramen, Paul Ewen, was punched, knocked to the ground and kicked by paratroopers he was filming.

ITN's Moscow bureau chief, Tim Ewart, said Ewen was able to return to work and his videotape was not seized.

Soviet troops also occupied an officers school in Kaunas, the republic's second-largest city, said the Lithuanian news agency.

Employees of the national guard building, formally known as the National Security Department, and Press House, where newspapers and other publications are printed, said troops ordered them to leave their offices. Witnesses said eight armored vehicles stood guard in front of the press building, including two tanks.

Tensions have been building in the Baltic republic since Monday, when the Defense Ministry announced that crack paratroopers would be used in Lithuania and six other rebellious republics to enforce the military draft.

Thousands of paratroopers have reportedly been activated, including 1,000 in Lithuania, the republic most advanced and radical in its independence drive. All the Soviet Union's 15 republics have declared independence or some form of sovereignty.

Ms. Dapkus, a spokeswoman for the Information Bureau of the Lithuanian parliament, said Soviet troops seized the National Security Department, three miles outside of Vilnius, early today. She said many employees of the department, responsible for security and defense within the republic, escaped.

Twenty minutes later, troops moved on the press center - the city's publishing house - and on the television tower, she said.

''The reaction of (Lithuanians) is very worried because there's shooting going on,'' she said.

Lithuanian Radio broadcast live reports of the troop movements, and Lithuanians flocked to the affected buildings, Ms. Dapkus said.

Hundreds of Lithuanian nationalists held an all-night vigil in and around the republic's parliament buildings. But hundreds of Russian factory workers who oppose Lithuanian independence also marched to the parliament today and tried to drown out the hundreds of Lithuanians singing patriotic songs and waving Lithuanian flags.

After Lithuania declared independence, Gorbachev imposed an economic embargo against the republic. He lifted the embargo last summer and agreed to hold talks after Lithuania agreed to put moves toward independence on hold.

Talks have failed to start after several attempts, reportedly contributing to the decision by Lithuanian Prime Minister Kazimiera Prunskiene to resign Tuesday, following a storm of protest over her government's price hikes.

The Lithuanian parliament late Thursday elected her successor, Albertas Simenas, a 40-year-old economist who was nominated by Landsbergis.

Simenas told the parliament that as long as there was no open Soviet aggression against Lithuania, he would try to develop Lithuanian-Soviet relations on the basis of full Lithuanian independence.