Anatoly Scharansky was brought to trial for treason here yesterday and strongly asserted his innocence in a case that could have historic consequences for Soviet-American relations.

Authorities disclosed that they have broadened the charge against Scharansky, whose fate has attracted world concern and the personal defense of President Carter. An accusation of anti-Soviet agitation and propaganda has been added to the charge of treason by espionage, which carries a possible death penalty.

Weatern journalists and diplomats, including U.S. embassy officials sent as an indication of Washington's concern, were barred from attending Scharansky's trial and that of another leading dissident, Alexander Ginzburg, which opened yesterday in Kaluga, 100 miles south of Moscow.Trials of two other persons charged with anti-Soviet activities also began yesterday.

The significance of the trials in U.S. Soviet relations has been greatly heightened by their timing, coming as U.S. Secretary of State Cyrus Vance and Soviet Foreign Minster Andrei Gromyko prepare to meet in Geneva tomorrow to discuss strategic arms limitations. The United States has already canceled two lower-level missions to the Soviet Union to show its displeasure with the trials.

Scharansky's indictment was disclosed in an unusual official press briefing for foreign journalists.

It alleges that Scharansky "betrayed his motherland" by passing defense secrets to foreign agents, by supplying "hostile materials" used by Western radio stations in anti-Soviet propaganda attacks and by attemptying to "pressure" the Kremlin to change its "internal and foreign policies." He exerted this pressure by such activities as writing letters to Sen. Henry M. Jackson (D-Wash.), the indictment charged.

"I'do not acknowledge any guildt and I consider the charges absurd," Scharansky, 30, declared to the court, according to his brother, Leonid, the only family member who was allowed to attend the first day's session.

Scharansky was "strong and self-confident," Leonid reported. He said Anatoly addressed the court for more than an hour during its morning session - despite admonitions from the presiding judge - saying that he believed he had acted in full accordance with international human rights agreements signed by the Kremlin and had violated no Soviet laws.

The drama of the Scharansky trial and its implicit challenge to Western critics and the human rights advocacy of President Carter was reinforced yesterday by the simultaneous opening elsewhere of two other Soviet dissident trial and another treason trial.

Ginzburg, twice-convicted human rights activits and administrator of a relief fund for political prisoners, professed his innocence of charges of anti-Soviet agitation and propaganda at his trial in Kaluga, a provincial city of about 100,000.

Ginzburg, 41, has "become an old man" after 18 months in jail, his wife said yesterday. He "said categorically that he was not guilty," she reported after being allowed to attend the session.

The indictment against Ginzburg alleges violation of Article 70 of the Soviet criminal code, in part because he possessed a copy of Alexander Solzhenitzyn's a "Gulag Archipelago," his famous study of the Stalin-era lobar camps, and "The Great Terror," a study of the Stalin-era purges of the 1930s in which millions died.

That possession of such works should constitute the basis for a criminal charge stands at the center of the Western criticism of the tactics and views of the Soviet government.

Meanwhile, dissident sources said, Viktoras Pyatkus, a Lithuanian dissident, was brought to trial yesterday in that Baltic republic's capital, Vilnius, on a similar charge of anti-Soviet agitation.

Thus , three members of Soviet groups set up in 1976 to monitor Soviet compliance with the human rights provisions of the Helsinki pact on European cooperation and security have been brought to the bar of Soviet justice in the climax the Kremlin's 18-month crackdown on political and religious dissenters.

The Tass news agency also reported yesterday that a man named Anatoli Filatov, described as an office worker, was brought to trial before a charge of treason by espionage similar to Scharansky's.

Dissidents said they did not know if there was any connection with the Scharansky case, and some speculated the trial might be related to recert Soviet allegations that it had uncovered a U.S. spy ring here.

According to Tass, Filatov was recruited by an unnamed foreign intelligence service while he served in Algeria in 1974 and "carried out espionage assignments in Moscow" until his arrest in 1977.

Tass said Filatov pleaded guilty and that the trial will continue."

But the attentions of virtually the entire Western community here were on the Scharansky trial, which began at 10 a.m. in a three-story brick people's court a few blocks from the Rossiya Hotel. Scharansky began his defense by himself after rejecting the aid of a government-appointed lawyer, Silva Dubrovskaya.

No foreign correspondent was allowed inside the court, hidden behind freshly painted wooden fences and steel police barricades manned by more than a hundred police and dozens of civilian guards. The only accounts of the proceedings come from either Leonid Scharansky of the government.

The indictment asserts that Scaharansky supplied state secrets to foreign agents, "including information on the location and security of a number of defense industry enterprises."

It said Robert C. Toth, a Los Angeles Times correspondent assigned here for three years until June 1977, was an American intelligence agent, an allegation Toth denied.

This allegation apprently centers on an article Toth wrote with the help of Scharansky, who was a friend, which reported place so employment of Jews who had been refused exit visas supposedly for security reasons.

The article said some had been employed in restaurants and other civilian establishments. Toth has said he wrote it to show the absurdity of Soviet rulings against jews refused permission to emigrate to Israel.

Toth said last night in a statement from New York, released by his paper's bureau here, that he "never worked for the Central Intelligence Agency or any other intelligence agency in my life. All the information collected in the Soviet Union was for publication in the Los Angeles Times. To allege I spied in any fashion is nonsense."

Soviet secret police seized Toth last year and questioned him closely on his relationship with Scharansky before allowing him to leave the country at the end of his assignment.

According to Leonid Scharansky, the indictment asserts that the prosecutor, Pyotr Solomin, plans to call Zinaida Popova, the Times' longtine secretary-translator, to "attest to the closeness of the relationship between Toth and Scharansky." Popova said last night she had never been contacted or questioned by the authorities and had no knowledge of being called as a prospective witness.

Leonid also said the indictment mentions a man identified as Alexander Zakharov, a laborer in the compound for foreigners where Toth lived, as having "found a list in Scharansky's handwriting" that will be introduced as evidence against him.

The Toth-Scharansky connection lies at the heart of the Kremlin's repeated attempts to protray American journalists here as secret agents for U.S. intelligence services. The Krelin says the journalists use dissident as spies and report their allegations of human rights inequilies in an unlawful effort to discredit the Soviet state.

The indictment, according to the briefing official, alleges that Scharansky systematically gave foreigners materials hostile to the state "in order to put pressure on the Soviet Union to change its internal and external policies."

Leonid Scharansky said prosecutor Solonin told the court that this material was used for "subversion" by Western radio stations such as the Voice of America, Radio Free Europe, Radio Liberty and the British Broad-casting Corp.

These station's powerful transmitters beam foreign correspondents' reports of dissient activities here, where they are never described in the official Soviet press, to what is thought to be millions of listeners.

The authorities have long sought to break this important connection linking dissidents, Western correspondents, the radio stations and the Soviet audience, despite the absence of any detectable sharing of dissident's views on the part of the vast mass of the people in this nation of more than 260 million.

The indictment also accused Scharansky of publicly calling on the U.S. Congress to approve the Jackson-Vanik amendment, which links U.S. Soviet trade to Kremlin policies on Jewish emigration.

Tass said he "admitted" these aims, and sent "at least 17 so-called documents, appeals, letters, and reviews, the main content of which were calls and incitements hostile to the U.S.S.R."

Leonid said his brother told the court that he would accept responsibility for any documents to which he had signed his name, or helped prepare, but denied they had anti-Soviet.