TURMOIL IN THE EAST BLOC : Church Bells Toll End of Dictatorship : Czechoslovakia: Dismantling of fence on Austrian border begins. Posters appear for start of presidential campaign.

PRAGUE, Czechoslovakia —  The deep bells began first--a long, slow pealing that echoed off the fairy-tale towers of St. Agnes’ Cathedral to mingle with a cacophony of automobile horns, a jangle of trolley bells and the whir of spinning noisemakers below.

For five minutes starting at noon Monday, the people of Prague made a joyful noise to celebrate their success in installing a new government that ended 41 years of Communist dictatorship.

Also on Monday, Czechoslovakia began to dismantle part of its Iron Curtain frontier with the West. Soldiers with trucks, machine shovels and wire cutters toiled in freezing weather on a five-mile section along the confluence of the Morava and Danube rivers dividing this country from Austria.

“The damned thing is going at last,” said a member of the army unit engaged in the work.

Czechoslovakia announced Nov. 30 that it would take down the barriers along its 240-mile southern frontier but has yet to disclose plans to remove those on its western border with West Germany.

As the new government got down to work, Prague witnessed the beginning of Czechoslovakia’s first public presidential election campaign in decades. Overnight, posters appeared in windows and on walls throughout the city bearing a black-and-white photograph of a smiling man wearing a sweater and jacket framed by a simple slogan:

“Havel na Hradna” --Havel to the Castle, the residence of Czechoslovak presidents.

Civic Forum, the country’s main opposition force, is backing its leader, Vaclav Havel, for the presidency, and as Czechoslovak political leaders met in round-table talks to discuss the issue, Havel’s political opponents seemed to be in disarray in their attempts to block him.

One indication of the high probability of Havel’s being elected came Monday night when Soviet television broadcast an interview with him, a portion of which was later aired on Czechoslovak national television. Havel made no particular news in the interview, but the interview itself was taken by many citizens here as a clear signal that the Kremlin is willing to accept Havel as Czechoslovakia’s head of state.

Under the country’s constitution, the Federal Assembly must elect a president by Dec. 24, two weeks from the day hard-line Communist Gustav Husak resigned as president. Havel has said he would serve only until elections are held next year, although he has not ruled out running at that point for a full five-year term.

The Havel posters simply added to the display of written material that has turned shop windows and the walls of Prague’s subway station into political libraries in the last three weeks. The city is covered with posters, manifestoes and declarations in all styles, from crudely scrawled posters in crayon and watercolor to mimeographed broad sheets to silk-screened works of art.

By twos and threes, Czechoslovaks, deprived for years of open political discussion, stop to read about the latest political debate or admire the once-forbidden satires.

One widely circulated poster depicts a signpost with arrows pointing in two directions. One arrow is labeled “ lid ,” the Czech word for people. The other arrow, which has a buzzard roosting on it, is labeled “ KSC ,” the initials in Czech for the Communist Party of Czechoslovakia. “Is there a Better Direction?” the caption asks.

At first, the posters focused almost exclusively on the nation’s political situation. But as the democracy movement has deepened here, all the political ferment of the West has begun to appear.

Monday, for example, Austrian environmental activists from Greenpeace were allowed for the first time to drive into Prague with a huge bus containing displays and literature opposing nuclear power. The Czechoslovaks have an ambitious nuclear power program that has generated strong opposition from anti-nuclear movements elsewhere in Europe.

“No CSSRnobyl,” reads the caption on a large yellow poster that Greenpeace has widely pasted up around Prague, blending the initials of the Czechoslovak Soviet Socialist Republic with the name of the Soviet nuclear power station where a severe accident occurred in April, 1986.

Over the weekend, for the first time, posters began to appear seeking support for a nascent homosexual rights movement here. The posters call for an end to discrimination and support for AIDS patients.

For now, however, most of the literature focuses on the presidential race. Several candidates are seeking the office, but only Havel has a solidified following.

The Communist Party newspaper Rude Pravo on Monday published a front-page article reporting a spate of “grass-roots” calls for former Prime Minister Ladislav Adamec to get the post.

But later in the day a leading member of the party Politburo appeared to rule out Adamec, telling reporters that the party agreed last week in round-table negotiations with opposition forces that the new president would not be a Communist Party member.

That condition was “the sort of macro-political ideas we agreed on,” Politburo member Ondrej Saling said.

Another Communist group announced support for Cesmir Cisar, a former party member who was purged after the 1968 Soviet invasion. Cisar was a prominent official during the Prague Spring reform effort squelched by that invasion.

And still another group, a reform Communist organization known as the Democratic Forum, called for the president to be elected directly, through a national ballot that would bypass Parliament, which is made up almost entirely of obedient, undistinguished Communist Party loyalists.

Parliament would probably elect Havel if the Communist leadership told it to do so, Democratic Forum leader Jaroslav Sedlack said. But a president elected that way would lack moral authority, he said.