The environmental disaster at the Chernobyl nuclear power plant is also rapidly turning into a public relations disaster for the new Soviet leader, Mikhail Gorbachev, who has been trying to impress European opinion with his pragmatism and openness.

Western officials and foreign policy analysts agree that the Kremlin's failure to provide detailed information about what has happened at Chernobyl could turn out to be almost as damaging for Moscow as the accident itself. The initial news blackout provoked protests from practically every government in Western Europe and raised concern among ordinary citizens on both sides of the "Iron Curtain."

The sparsity of official Soviet information has served to underline one of the key differences between the Soviet Union, where the mass media are rigidly controlled, and the pluralist societies of the West.

"This will undoubtedly harm Gorbachev with western public opinion," noted an adviser to French Prime Minister Jacques Chirac. "First, it confirms the impression that the Soviets are incredibly sloppy in the way they use technology. Second, it is a reminder of the way in which a totalitarian system operates."

As if to compound Gorbachev's problems, the radioactive cloud released by the Chernobyl plant following the accident cut across politically sensitive areas for the Kremlin -- including the Soviet Baltic republics of Latvia and Lithuania, where nationalist sentiment runs high, and Poland. After protruding into Scandinavia at the weekend, it was heading toward the neutral countries of Austria and Switzerland.

Switzerland, which traditionally is reluctant to criticize Moscow publicly, joined other West European countries today in condemning the Soviet Union for waiting until higher than normal levels of radiation were noticed in Scandinavia to confirm that an accident had taken place.

Edouard Brunner, the number two man in the Swiss Foreign Ministry, described the delay as "astounding." He noted that the 1975 Helsinki declaration provided for a "free flow of information" on such matters.

Several Europeans commented that the Soviet handling of the disaster was particularly damaging to Gorbachev because it contrasted with the modern image he has sought to project since he came to power in March 1985. He has scored political points in Western Europe recently with his repeated appeals for a moratorium on nuclear tests, which have been rejected by the United States.

A pointed reminder of the gap between words and deeds was provided by a British Foreign Office minister, Tim Eggar, who said the "lesson" of the Chernobyl incident was that "the openness which Gorbachev has said is necessary in Soviet society must become a reality." He was speaking in a debate in the House of Commons in which politicians of both left and right expressed concern about the potential health hazards.

Some officials said they believed negative public reaction to the disaster in Western Europe could tarnish the Soviet Union in the eyes of ecologists and pacifists, the very constituency that Gorbachev has been most successful in wooing.

The Soviet Union's handling of the accident has parallels with the shooting down of a South Korean airliner with 269 people on board in September 1983. On that occasion, Moscow at first denied it had taken place and then waited five days before acknowledging that the airliner had been intercepted by Soviet fighter planes. Much of the information that the Soviet government did eventually provide was in response to details that had already emerged in the West.

In neighboring communist Poland, where the government faces the problem of calming an alarmed population, the approach this time has differed from Moscow's. Although the officially controlled Polish news media have stuck closely to the Soviet version of the accident, they have gone into considerable detail in pressing medical precautions, such as restricting sales of milk and washing fruit and vegetables.

By western standards, the information available to Poles living some 300 miles from the site of the disaster seems slim. But it is considerably more detailed than that provided to Soviet citizens closer to Chernobyl.

In an apparently coordinated effort, Soviet ambassadors in many West European capitals called on government officials today to allay fears about the extent of the disaster. Like the United States, most West European governments have offered to provide expertise in fighting a graphite fire or treating victims.

West European newspapers were uniformly critical of the Soviet handling of the disaster. In a typical comment, the Stockholm daily Svenska Dagbladet said that Soviet society was "far too primitive to use such a sophisticated technique as nuclear power."

The Zurich newspaper Tages Anzeiger said that the disaster illustrated "not only the weaknesses and deficiencies of the Soviet system, but also the incredible danger that arises from the isolation of a nation, especially a superpower."

The leftist French newspaper Liberation commented that "Communists make electricity like they make war -- without worrying too much about victims and by eliminating observers."