MOSCOW, FEB. 2 -- Tatyana Mitkova, the host of a popular late-night television news show, can date the demise of glasnost precisely. It happened shortly after midnight on Jan. 14, 1991, just as she was about to go on the air with a report on the Soviet military crackdown in Lithuania.

The deputy head of Soviet television, Pyotr Reshetov, had made a rare appearance in the newsroom a half-hour earlier; he glanced over Mitkova's work, crossed out 12 pages and sat down at a typewriter to produce the official version of what had taken place in Lithuania. The new script was handed to Mitkova with two minutes left to air time. She refused to accept it, so a staff announcer was ordered to read it instead.

"We have become a state television service controlled by censors," said Mitkova, one of a team of American-style news anchors who have sought to revolutionize Soviet television journalism by stressing the importance of fact over opinion. "If you have information that you want to broadcast, and someone prevents you from doing so, I call that censorship."

As the political battle over the future of the Soviet Union intensifies, the nation's television studios and newspaper offices seem to be straddling the front lines -- quite literally, in some places. Last month, Soviet paratroops stormed Lithuania's main television station and transmission tower, using automatic rifles and tanks to break through crowds surrounding the buildings and killing 13 unarmed civilians in the process.

Here in Moscow, the hostilities have been ideological rather than physical. Confident that events are moving in their direction, Communist Party hard-liners are attempting to reassert central control over the mass media. President Mikhail Gorbachev, who made glasnost -- openness -- his own political slogan, has raised the possibility of suspending press freedoms to ensure journalistic "objectivity."

Today, broadcasting authorities took action against the principal radio station of the Soviet Union's vast Russian republic, depriving it of most of its transmission frequencies. A spokesman for Radio Russia, which was launched last year, said the move followed complaints by Gorbachev about its coverage of the army action in Lithuania and the other secessionist Soviet Baltic republics.

The battle between journalists and censors at Moscow's "Television News Service" -- known by its Russian initials as "TSN" -- has mirrored a much broader struggle to rescue the Soviet Union's fledgling democracy. For a few days after the military went into action in Lithuania, censorship was exceptionally tight, but it has relaxed somewhat over the past week, and the long-term outcome of the battle is still in doubt.

"TSN" was launched a year ago to compete with the official 9 p.m. evening news program, "Vremya." It quickly gained a reputation for informative, concise reporting and independent news judgment. Unlike "Vremya," which routinely leads the news with whatever Gorbachev has been doing over the past 24 hours, "TSN" immediately zeroes in on what it considers the most important story of the day.

"We try to give viewers a picture of what is really happening in the world through the eyes of the anchor. Everything has been going pretty well for the past year. We were occasionally criticized for our reporting, but there was no pre-censorship," said Yuri Rostov, one of the anchors.

The first sign of a tightening of official controls came in December with the appointment of Leonid Kravchenko as head of Gostelradio, the state broadcast-media committee. An orthodox Communist Party bureaucrat, Kravchenko has made no secret of the fact that he regards television as a political instrument of Gorbachev, and he personally blocked the popular news show "Vzglyad" from airing a program on the dramatic resignation of foreign minister Eduard Shevardnadze and his warnings of "coming dictatorship."

There were other straws in the wind, too. A few weeks ago, "Vremya" abruptly jettisoned its new, glasnost-era signature tune without explanation. It was replaced by the old tune, an ideologically uplifting march intended to underscore the daily triumphs of socialism. Whatever the reason behind the switch, the message conveyed to millions of Soviet television viewers was that the old days were returning.

At "TSN," whose offices are just down the corridor from "Vremya," the atmosphere became more strained after the New Year. On Jan. 4, Rostov was suspended after telling viewers that "Vzglyad" had been canceled as a result of the abortive Shevardnadze program. But it was not until Jan. 13, the night of the army action in Vilnius, the Lithuanian capital, that prior censorship was effectively reintroduced.

At first, senior Gostelradio officials intervened directly to tell the "TSN" team what could and could not be broadcast. Then, familiar old functionaries from pre-glasnost days called glavni vuipuskayuschii -- literally, "chief releasers" -- began reappearing around the newsroom. The word "censorship" is studiously avoided, but all scripts are now submitted to the releasers for approval.

"Mitkova is exaggerating things," said Gostelradio news director Olvar Kakuchaya. "We're not talking about censorship; we're simply trying to prevent ad-libbing."

Unlike the youthful "TSN" team, most of whom are in their early thirties, the releasers are elderly bureaucrats brought back from retirement. Several had worked for many years at Moscow Radio, holding what one newspaper delicately described as "analogous positions." Relations between the releasers and the rest of the "TSN" staff are polite, but frigid.

"TSN" anchors insist that the releasers are suppressing not only opinions but genuine news. As evidence, they point to what happened Jan. 16, when an entire program was canceled because of an item on the fatal police shooting of a motorist in Riga, the Latvian capital. It was the first violent incident in the Baltics involving an elite Soviet police unit known as "Black Berets," who four days later went on to storm the Latvian Interior Ministry, an attack that left four Latvians dead.

"We had pictures, images, right down to the bullet in the skull on X-ray photos that we obtained from the hospital. The world's news agencies had already reported this fact, but we were forbidden to use it," said anchorman Dmitri Kisilev. "You can say that glasnost was buried during these days."

As Gorbachev moved to distance himself from the military actions in the Baltic republics and to assert that all problems should be resolved through negotiation, the bureaucratic pressure on "TSN" seemed to ease. No punitive action has been taken against any of the "TSN" anchors who have denounced the new censoring procedures in numerous interviews with Soviet and foreign journalists.

"TSN," like the Soviet Union itself, seems to have entered a twilight zone. The heady days of glasnost have gone, but there has been no general return to old-style repression. By the standards of the pre-Gorbachev era, censorship is still relatively light and largely limited to the broadcast media.

What will happen next is unclear. Mitkova insists that the attempt to suppress information cannot last. "There's no need to despair. This is the death agony of a sick organism," she told the weekly newspaper Moscow News recently.

Others take a more pessimistic view, predicting further assaults on press freedom over the coming months. An army colonel now reads the news on Vilnius television, a grim harbinger of what could happen in the rest of the country if there is a full-scale military crackdown. And on Leningrad television, well-known commentator Alexander Nevzorov adopted a stridently nationalist tone, suggesting in a series of provocative programs that ethnic Russians living in the Baltic republics are in danger of annihilation by separatists there.

"A huge battle is going on, and we don't know who is going to win," said Vitaly Tishkin, a senior "TSN" editor. "But even if we end up with a hard-line regime, I think it will be a different kind of regime from the one we had before. To return to the previous state of affairs is impossible."